JP7586007B2 - Semiconductor light emitting device and method for manufacturing the same - Google Patents

Description

The present invention relates to a semiconductor light-emitting device and a method for manufacturing the semiconductor light-emitting device.

In recent years, the market for display devices such as projectors that use semiconductor lasers has been expanding. When using semiconductor lasers in display devices, there is a demand for monolithic lateral single mode semiconductor lasers that independently drive multiple light emitting layers (multiple light emitting layers) with narrow pitch in order to improve image quality such as resolution and frame rate.

Patent document 1 discloses a multi-wavelength semiconductor laser capable of oscillating lasers of multiple wavelengths within the same element. In the technology of Patent document 1, in an AlGaAs-based quantum well laser, the well width (physical film thickness) of the first and second quantum well active layers is made different to achieve multi-wavelength. Specifically, after forming an insulating film on a semiconductor substrate, the insulating film in the element formation region is removed by etching, and then epitaxial growth is performed on the entire semiconductor substrate including the insulating film. At this time, epitaxial growth is not performed on the insulating film, but selective epitaxial growth is performed on the part where the insulating layer has been etched away. In addition, the film thickness of the element formed by epitaxial growth can be adjusted according to the width of the insulating layer and the width of the region removed by etching. Such a technology is known and is called the selective growth method.

Japanese Patent Application Publication No. 05-082894

However, in the method disclosed in Patent Document 1, if an AlGaInP-based material is used to achieve an oscillation wavelength in the red region, the composition shift during selective growth can increase lattice mismatch, and there is a risk that the light emission efficiency and lifespan of the laser can decrease.

The object of the present invention is to provide a monolithic semiconductor light-emitting device and a method for manufacturing the semiconductor light-emitting device that can emit laser light having different wavelengths while suppressing lattice mismatch that occurs when using selective growth methods.

A semiconductor light-emitting device according to one aspect of the present invention includes a first conductive clad layer, an insulating layer that divides the first conductive clad layer, m (m is an integer of 2 or more) light-emitting layers that are stacked on the first conductive clad layer divided by the insulating layer and emit laser light of different wavelengths, m second conductive clad layers that are stacked on the m light-emitting layers, and a polycrystalline semiconductor layer that is stacked on the insulating layer.

This allows the device to be formed without reducing the selectivity of the selective growth method in the areas where no insulating layer is provided when the light-emitting layer is formed. Furthermore, by adjusting the material composition so that it can be laminated on the insulating layer, a polycrystalline semiconductor layer can be formed on the insulating layer, and the selectivity of the selective growth method when the second conductive cladding layer is formed can be reduced, and the composition of the second conductive cladding layer laminated on each of the m light-emitting layers can be made uniform. Therefore, while making it possible to make the oscillation wavelengths of the m light-emitting layers different, it is possible to suppress the lattice mismatch between the compound semiconductor substrate made of GaAs or the like and the second conductive cladding layer, and it is possible to suppress the decrease in light-emitting efficiency and life while realizing a monolithic multi-wavelength semiconductor laser that can be driven independently.

In addition, by stacking the second conductive clad layer on the m light-emitting layers while depositing a polycrystalline semiconductor layer on the insulating layer that divides the first conductive clad layer, it is not necessary to remove the insulating layer to suppress lattice mismatch between the compound semiconductor substrate and the second conductive clad layer. Therefore, the second conductive clad layer can be continuously formed on the m light-emitting layers without exposing the light-emitting layers to the atmosphere, and deterioration of the crystal quality of the second conductive clad layer can be suppressed.

In addition, in the semiconductor light-emitting device according to one aspect of the present invention, the polycrystalline semiconductor layer contains the constituent elements of the second conductivity type cladding layer as a main component.

This allows the polycrystalline semiconductor layer to be formed on the insulating layer at the same time as the second conductive cladding layer is formed. This allows the composition of the second conductive cladding layers stacked on each of the m light emitting layers to be uniform, and lattice mismatch between the compound semiconductor substrate and the second conductive cladding layer to be suppressed.

In the semiconductor light emitting device according to an aspect of the present invention, the light emitting layer contains ( _{AlxGa1 -x} ) _{1- yInyP} (0≦x<1, 0<y<1).

This makes it possible to set the oscillation wavelength of the m light-emitting layers in the red region, and by lowering the Al composition x, it is possible to increase the selectivity in the selective growth method when forming the light-emitting layers. This makes it possible to use the semiconductor laser as a light source for a display device, and to realize a monolithic multi-wavelength semiconductor laser that can be driven independently, thereby reducing the coherence of the transverse single mode laser and improving the image quality of the display device.

In the semiconductor light emitting device according to an aspect of the present invention, the second conductivity type cladding layer is made of ( _{AlxGa1 -x} ) _{1- yInyP} (0<x≦1, 0<y<1).

This makes it possible to reduce the selectivity in the selective growth method when forming the second conductive cladding layer. Therefore, when forming the second conductive cladding layer, a polycrystalline semiconductor layer can be formed on the insulating layer at the same time, and the composition of the second conductive cladding layer laminated on each of the m light emitting layers can be made uniform. In addition, the film thickness of the second conductive cladding layer on each light emitting layer can be made uniform, and the monolithic multi-wavelength semiconductor laser can be mounted by junction down bonding on a submount on which an electrode is arranged. This makes it possible to improve the heat dissipation of the monolithic multi-wavelength semiconductor laser, and to improve the reliability of the monolithic multi-wavelength semiconductor laser.

In addition, in the semiconductor light emitting device according to one aspect of the present invention, the difference in Al composition x between the (Al _x Ga _1-x ) _1-y In _y P used in each of the m second conductive type cladding layers is smaller than the difference in Al composition x between the (Al _x Ga _1-x ) _1-y In _y P used in each of the m light emitting layers.

This allows the selectivity in the selective growth method to be reduced when forming the second conductive cladding layer without reducing the selectivity in the selective growth method when forming the light emitting layer. This makes it possible to suppress lattice mismatch between the compound semiconductor substrate and the second conductive cladding layer while making it possible to differentiate the oscillation wavelengths of the m light emitting layers.

In addition, according to one aspect of the semiconductor light-emitting device of the present invention, the widths of the m light-emitting layers on the first conductive cladding layer partitioned by the insulating layer are different from each other.

By forming openings with different opening widths in the insulating layer on the first conductive type cladding layer, the quantum well widths of the m light-emitting layers formed on the first conductive type cladding layer can be made different from each other. Therefore, m light-emitting layers with different oscillation wavelengths can be formed collectively on the first conductive type cladding layer, and it is no longer necessary to repeatedly form the light-emitting layers in order to form m light-emitting layers with different oscillation wavelengths. As a result, it is possible to realize a monolithic multi-wavelength semiconductor laser that can be driven independently while suppressing an increase in the number of processes.

In addition, according to one aspect of the semiconductor light-emitting device of the present invention, the quantum well widths of the m light-emitting layers are different from each other.

This allows the oscillation wavelengths of the m light-emitting layers to be different, realizing a monolithic multi-wavelength semiconductor laser that can be driven independently.

In addition, according to a semiconductor light-emitting device according to one aspect of the present invention, the insulating layer contains at least one oxide, nitride, or mixture of Si, Mg, Al, Hf, Nb, Zr, Sc, Ta, Ga, Zn, Y, B, and Ti.

This makes it possible to prevent the light-emitting layer from being formed on the insulating layer, and also prevents contamination by the insulating layer when forming the light-emitting layer and the second conductive cladding layer, thereby preventing a deterioration in crystal quality.

In addition, in the semiconductor light-emitting device according to one aspect of the present invention, the height position of the interface between the insulating layer and the first conductive cladding layer is equal to the height position of the interface between the light-emitting layer and the first conductive cladding layer.

In this way, openings with different opening widths are formed in the insulating layer on the first conductive cladding layer, and then a light-emitting layer is formed on the first conductive cladding layer exposed in the openings, so that the height of the upper surface of each layer formed thereafter can be made equal to that of the insulating layer portion, ensuring flatness. Also, by leaving the insulating layer as it is, an increase in the number of processes can be suppressed.

In addition, according to a semiconductor light-emitting device according to one aspect of the present invention, the height position of the interface between the insulating layer and the first conductive cladding layer can be higher than the height position of the interface between the light-emitting layer and the first conductive cladding layer.

As a result, openings with different opening widths are formed in the insulating layer on the first conductive type clad layer, and then contaminants or defects on the surface of the first conductive type clad layer exposed through the openings are removed, and then a light-emitting layer can be formed on the first conductive type clad layer, thereby improving the crystal quality of the light-emitting layer.

In addition, according to one aspect of the semiconductor light-emitting device of the present invention, the height position of the interface between the insulating layer and the first conductive cladding layer can be lower than the height position of the interface between the light-emitting layer and the first conductive cladding layer.

This allows openings of different widths to be formed in the insulating layer on the first conductivity type cladding layer, and then the first conductivity type cladding layer is regrown on the first conductivity type cladding layer exposed through the opening, and then the light-emitting layer is formed on the first conductivity type cladding layer. Therefore, even if the first conductivity type cladding layer is exposed to the atmosphere in a process before the light-emitting layer is formed, it is possible to prevent the light-emitting layer from coming into direct contact with the surface of the first conductivity type cladding layer that has been contaminated by exposure to the atmosphere, and the crystal quality of the light-emitting layer can be improved.

In addition, a method for manufacturing a semiconductor light-emitting device according to one aspect of the present invention includes the steps of forming a first conductive type cladding layer on a compound semiconductor substrate, forming a mask having m (m is an integer of 2 or more) openings with different opening widths on the first conductive type cladding layer, selectively growing a light-emitting layer on the first conductive type cladding layer in the openings, and stacking a second conductive type cladding layer on the light-emitting layer while depositing a polycrystalline semiconductor layer on the mask.

This makes it possible to differentiate the oscillation wavelengths of the m light-emitting layers without repeatedly depositing the light-emitting layers, and also makes it possible to suppress lattice mismatch between the compound semiconductor substrate and the second conductivity type cladding layer without exposing the light-emitting layers to the atmosphere. This makes it possible to realize m independently operable monolithic multi-wavelength semiconductor lasers while suppressing an increase in the number of processes, and also makes it possible to suppress a decrease in light-emitting efficiency and life span.

In addition, according to one aspect of the present invention, the method for manufacturing a semiconductor light-emitting device further includes a step of etching or cleaning the first conductive cladding layer in the region of the opening, and a step of selectively growing the light-emitting layer on the etched surface or cleaned surface of the first conductive cladding layer.

As a result, after forming openings with different opening widths in the insulating layer on the first conductive type clad layer, a light-emitting layer can be formed on the etched or cleaned surface from which contaminants or defects on the surface of the first conductive type clad layer exposed through the openings have been removed, thereby improving the crystal quality of the light-emitting layer.

In addition, according to one aspect of the present invention, the method for manufacturing a semiconductor light-emitting device further includes a step of regrowing the first conductive type cladding layer in the opening, and a step of selectively growing the light-emitting layer on the regrown surface of the first conductive type cladding layer.

This allows openings with different opening widths to be formed in the insulating layer on the first conductive cladding layer, and then the light-emitting layer can be continuously formed on the regrown surface of the first conductive cladding layer exposed in the area of the opening, thereby improving the crystal quality of the light-emitting layer.

In one aspect of the present invention, it is possible to provide a monolithic semiconductor light-emitting element capable of emitting laser light of different wavelengths while suppressing lattice mismatch.

1 is a perspective view showing a schematic configuration of a semiconductor light emitting device according to a first embodiment. 6A to 6C are cross-sectional views showing an example of a method for manufacturing a semiconductor light emitting device according to a second embodiment. 6A to 6C are cross-sectional views showing an example of a method for manufacturing a semiconductor light emitting device according to a second embodiment. 6A to 6C are cross-sectional views showing an example of a method for manufacturing a semiconductor light emitting device according to a second embodiment. 6A to 6C are cross-sectional views showing an example of a method for manufacturing a semiconductor light emitting device according to a second embodiment. 6A to 6C are cross-sectional views showing an example of a method for manufacturing a semiconductor light emitting device according to a second embodiment. 6A to 6C are cross-sectional views showing an example of a method for manufacturing a semiconductor light emitting device according to a second embodiment. 10A to 10C are cross-sectional views showing an example of a method for manufacturing a semiconductor light emitting device according to a third embodiment. 10A to 10C are cross-sectional views showing an example of a method for manufacturing a semiconductor light emitting device according to a 10A to 10C are cross-sectional views showing an example of a method for manufacturing a semiconductor light emitting device according to a third embodiment. 10A to 10C are cross-sectional views showing an example of a method for manufacturing a semiconductor light emitting device according to a third embodiment. 10A to 10C are cross-sectional views showing an example of a method for manufacturing a semiconductor light emitting device according to a third embodiment. 10A to 10C are cross-sectional views showing an example of a method for manufacturing a semiconductor light emitting device according to a third embodiment. 10A to 10C are cross-sectional views showing an example of a method for manufacturing a semiconductor light emitting device according to a third embodiment. 10A to 10C are cross-sectional views showing an example of a method for manufacturing a semiconductor light emitting device according to a fourth embodiment. 10A to 10C are cross-sectional views showing an example of a method for manufacturing a semiconductor light emitting device according to a fourth embodiment. 10A to 10C are cross-sectional views showing an example of a method for manufacturing a semiconductor light emitting device according to a fourth embodiment. 10A to 10C are cross-sectional views showing an example of a method for manufacturing a semiconductor light emitting device according to a fourth embodiment. 10A to 10C are cross-sectional views showing an example of a method for manufacturing a semiconductor light emitting device according to a fourth embodiment. 10A to 10C are cross-sectional views showing an example of a method for manufacturing a semiconductor light emitting device according to a fourth embodiment. 10A to 10C are cross-sectional views showing an example of a method for manufacturing a semiconductor light emitting device according to a fourth embodiment.

Below, the embodiments of the present invention will be described in detail with reference to the attached drawings. Note that the following embodiments do not limit the present invention, and not all of the combinations of features described in the embodiments are necessarily essential to the configuration of the present invention. The configuration of the embodiments may be modified or changed as appropriate depending on the specifications of the device to which the present invention is applied and various conditions (usage conditions, usage environment, etc.). The technical scope of the present invention is determined by the claims, and is not limited by the individual embodiments below. Also, the drawings used in the following description may differ in scale and shape from the actual structure in order to make each configuration easier to understand.

First Embodiment
FIG. 1 is a perspective view showing a schematic configuration of a semiconductor light emitting device according to the first embodiment. In the following description, a monolithic multi-wavelength semiconductor laser having three light emitting layers emitting laser beams of different wavelengths is taken as an example, but a monolithic multi-wavelength semiconductor laser having m (m is an integer of 2 or more) light emitting layers emitting laser beams of different wavelengths may be used. In the following description, a semiconductor laser having multiple wavelengths in the red region is taken as an example, but the present invention is not necessarily limited to a semiconductor laser having multiple wavelengths in the red region. In the example of FIG. 1, for simplification, a compound semiconductor substrate on which the monolithic multi-wavelength semiconductor laser is formed and an electrode for injecting a current into the light emitting layer are omitted.

In FIG. 1, the semiconductor laser Z0 includes an n-type cladding layer N, light-emitting layers A1 to A3, and p-type cladding layers B1 to B3. Although not shown in FIG. 1, the n-type cladding layer N is formed on a compound semiconductor substrate, and a GaAs substrate is used in this embodiment. At this time, each of the light-emitting layers A1 to A3 can form a double heterojunction between the n-type cladding layer N and each of the p-type cladding layers B1 to B3. Each of the light-emitting layers A1 to A3 emits laser beams L1 to L3 having different wavelengths. Here, in order to set the wavelength of each of the laser beams L1 to L3 in the red region, each of the light-emitting layers A1 to A3 can include (Al _x Ga _1-x ) _1-y In _y P (0≦x<1, 0<y<1).

The n-type cladding layer N is divided into partition regions E1 to E3 by an insulating layer M. Each partition region E1 to E3 is provided along the optical waveguide direction of each light-emitting layer A1 to A3. At this time, each light-emitting layer A1 to A3 is separated by the insulating layer M. The insulating layer M can contain at least one oxide, nitride, or mixture of Si, Mg, Al, Hf, Nb, Zr, Sc, Ta, Ga, Zn, Y, B, and Ti. By using such a material, it is possible to prevent materials from being stacked on the insulating layer M when forming each light-emitting layer A1 to A3. In addition, since the p-type cladding layers B1 to B3 are formed without removing the insulating layer M after forming each light-emitting layer A1 to A3, contamination by the insulating layer M can be prevented, and deterioration of crystal quality can be prevented.

The widths W1 to W3 of the light-emitting layers A1 to A3 are different from each other. In this case, the widths of the partitioned regions E1 to E3 can be made equal to the widths W1 to W3 of the light-emitting layers A1 to A3. For example, the widths W1 to W3 of the light-emitting layers A1 to A3 can be set to W1<W2<W3.

Each of the light-emitting layers A1 to A3 includes an active layer A1B to A3B. Each of the active layers A1B to A3B may have a multi-quantum well (MQW) structure in which a barrier layer and a well layer are alternately stacked. Each of the light-emitting layers A1 to A3 may include a guide layer A1A to A3A below each of the active layers A1B to A3B, and a guide layer A1C to A3C above each of the active layers A1B to A3B. Each of the guide layers A1A to A3A and A1C to A3C can guide the laser light guided through each of the active layers A1B to A3B. In this case, the thickness of each of the guide layers A1A to A3A and A1C to A3C can be made thicker than the thickness of the barrier layer of each of the active layers A1B to A3B. Each of the guide layers A1A-A3A, A1C-A3C is sometimes called an SCH (Separate Confinement Heterostructure) layer or confinement layer, and has a higher refractive index than the n-type cladding layer N and the p-type cladding layers B1-B3, and a lower refractive index than each of the active layers A1B-A3B.

By making the widths W1 to W3 of the light-emitting layers A1 to A3 different from one another, the quantum well widths of the active layers A1B to A3B can be made different from one another, and the wavelengths of the laser lights L1 to L3 can be made different from one another. By making the wavelengths of the laser lights L1 to L3 different by about several nm, the coherence of the transverse single mode laser can be reduced, and the image quality can be improved when the semiconductor laser Z0 is used as a light source for a display device.

On each of the light-emitting layers A1 to A3, p-type clad layers B1 to B3 are laminated. Ridges G1 to G3 are formed in each of the p-type clad layers B1 to B3 along the optical waveguide direction of each of the light-emitting layers A1 to A3. Here, each of the p-type clad layers B1 to B3 may be composed of p-type clad layers B1A to B3A and B1C to B3C separated vertically with etch stop layers B1B to B3B in between. The etch stop layers B1B to B3B can define the stop position of etching in the thickness direction of the p-type clad layers B1 to B3 to form the ridges G1 to G3. At this time, the ridges G1 to G3 can be composed of p-type clad layers B1C to B3C. Cap layers C1 to C3 are provided on the p-type clad layers B1C to B3C. The cap layers C1 to C3 can make ohmic contact with an electrode that injects current into each of the light-emitting layers A1 to A3.

Here, the p-type cladding layers B1 to B3 can be composed of (Al _x Ga _1-x ) _1-y In _y P (0<x≦1, 0<y<1) in order to reduce the lattice mismatch with the compound semiconductor substrate. The difference in Al composition x between the (Al _x Ga _1-x ) _1-y In _y P used in each of the p-type cladding layers B1 to B3 can be made smaller than the difference in Al composition x between the (Al _x Ga _1-x ) _1-y In _y P used in each of the light-emitting layers A1 to A3. The etch stop layers B1B to B3B have a lower etching rate than the p-type cladding layers B1A to B3A and B1C to B3C, so that the Al composition x can be made lower than that of the p-type cladding layers B1A to B3A and B1C to B3C.

A polycrystalline semiconductor layer P is deposited on the insulating layer M. The polycrystalline semiconductor layer P includes the polycrystalline structure of the p-type cladding layers B1 to B3. In this case, the polycrystalline semiconductor layer P can include the constituent elements of the p-type cladding layers B1 to B3 as the main components. In this case, the formation of the p-type cladding layers B1 to B3 on each of the light-emitting layers A1 to A3 and the deposition of the polycrystalline semiconductor layer P on the insulating layer M can be performed simultaneously. The polycrystalline semiconductor layer P may include the polycrystalline structure of the etch stop layers B1B to B3B and the polycrystalline structure of the cap layers C1 to C3.

Here, by increasing the Al composition x when the p-type cladding layers B1 to B3 are composed of (Al _x Ga _1-x ) _1-y In _y P, it is possible to reduce the selectivity in the selective growth method when the p-type cladding layers B1 to B3 are formed. Therefore, it is possible to deposit a polycrystalline semiconductor layer P on the insulating layer M when the p-type cladding layers B1 to B3 are formed on the light-emitting layers A1 to A3. It is to be noted that even when the etch stop layers B1B to B3B having a low Al composition x are present in the p-type cladding layers B1 to B3, the polycrystalline semiconductor layer P can be deposited on the insulating layer M.

At this time, the selectivity in the selective growth method is reduced when forming the p-type cladding layers B1 to B3, and the formation of the p-type cladding layers B1 to B3 on each of the light-emitting layers A1 to A3 and the deposition of the polycrystalline semiconductor layer P on the insulating layer M are simultaneously performed, thereby making it possible to homogenize the composition of the p-type cladding layers B1 to B3. This makes it possible to suppress lattice mismatch between the compound semiconductor substrate and the p-type cladding layers B1 to B3, and to suppress a decrease in the light-emitting efficiency and lifespan of the semiconductor laser Z0.

Moreover, by forming each of the light emitting layers A1 to A3 from (Al _x Ga _1-x ) _1-y In _y P (0≦x<1, 0<y<1) and making the Al composition x of each of the light emitting layers A1 to A3 lower than the Al composition x of the p-type cladding layers B1 to B3, it is possible to reduce the selectivity in the selective growth method when forming the p-type cladding layers B1 to B3 without reducing the selectivity in the selective growth method when forming the light emitting layers A1 to A3. This makes it possible to make the oscillation wavelengths of each of the light emitting layers A1 to A3 different, thereby realizing a monolithic multi-wavelength semiconductor laser that can be driven independently.

In addition, by reducing the selectivity in the selective growth method when forming the p-type cladding layers B1 to B3, the thickness of the p-type cladding layers B1 to B can be made uniform, and even when the semiconductor laser Z0 is mounted by junction down bonding on a submount on which electrodes are arranged, no steps are created between the ridges, and the semiconductor laser Z0 can be closely attached to the submount. This improves the heat dissipation of the semiconductor laser Z0, thereby improving its reliability.

In addition, by reducing the selectivity in the selective growth method when forming the p-type cladding layers B1 to B3, even when the insulating layer M exists on the n-type cladding layer N, the p-type cladding layers B1 to B3 can be continuously formed on each of the light-emitting layers A1 to A3 in the same chamber while suppressing the lattice mismatch between the compound semiconductor substrate and the p-type cladding layers B1 to B3. Therefore, it is no longer necessary to remove the insulating layer M in order to suppress the lattice mismatch between the compound semiconductor substrate and the p-type cladding layers B1 to B3, and it is possible to form the p-type cladding layers B1 to B3 without exposing each of the light-emitting layers A1 to A3 to the atmosphere. As a result, it is possible to suppress the deterioration of the crystal quality of the p-type cladding layers B1 to B3.

Second Embodiment
2A to 2F are cross-sectional views showing an example of a method for manufacturing a semiconductor light-emitting device according to the second embodiment, in which FIG. 2A to FIG. 2F show views corresponding to a cross section taken along line DA-DA in the semiconductor laser Z0 shown in FIG. 1 as Example 1.

In FIG. 2A, an n-type cladding layer N is formed on a compound semiconductor substrate S by epitaxial growth. The epitaxial growth may be MOCVD (Metal Organic Chemical Vapor Deposition), MBE (Molecular Beam Epitaxy), or HVPE (Hydride Vapor Phase Epitaxy). The compound semiconductor substrate S is, for example, a GaAs substrate. The thickness of the n-type cladding layer N can be set to, for example, about 2 μm.

The composition of the n-type cladding layer N can be adjusted, for example, to 0.5, in order to lattice match with the GaAs substrate, in (Al _x Ga _1-x ) _1-y In _y P. In order to make the refractive index of the n-type cladding layer N smaller than the refractive index of each of the light-emitting layers A1 to A3, the composition ratio x:1-x of Al and Ga can be adjusted to x:1-x=1:0, with the Al composition x being larger.

Next, an insulating layer M is formed on the n-type cladding layer N by a method such as plasma CVD (Chemical Vapor Deposition) or sputtering. The insulating layer M may be, for example, _SiO2 , SiN, or _Al2O3 . The thickness of the insulating layer M may be set to be approximately the same as the thickness of the light-emitting layer _A1 , for example, 100 nm. In order to relieve the film stress of the insulating layer M, the thickness of the insulating layer M may be thinned to about several nm.

Next, the insulating layer M is patterned by using photolithography and etching techniques to form openings V1 to V3 with different opening widths in the insulating layer M. This etching can be, for example, dry etching such as RIE (Reactive Ion Etching). Alternatively, patterning may be performed by wet etching. The openings V1 to V3 can be formed in a stripe shape along the optical waveguide direction of each of the light-emitting layers A1 to A3. Masks M1 to M4 in which the insulating layer M is separated by the openings V1 to V3 can be formed on the n-type clad layer N. The crystalline growth of each of the light-emitting layers A1 to A3 is inhibited on the masks M1 to M4. Here, the masks M1 to M4 can define the partitioned regions E1 to E3 in which each of the light-emitting layers A1 to A3 is formed. At this time, the opening width of the openings V1 to V3 can define the width of the partitioned regions E1 to E3. The mask width of each mask M1 to M4 can be set to, for example, 5 μm, 50 μm, 30 μm, or 15 μm.

Next, as shown in Fig. 2B, the light emitting layers A1 to A3 are selectively formed on the n-type cladding layer N exposed in the regions of the openings V1 to V3 by epitaxial growth. At this time, the guide layers A1A to A3A, active layers A1B to A3B, and guide layers A1C to A3C in Fig. 1 can be sequentially formed as the light emitting layers A1 to A3. Here, by lowering the Al composition x of (Al _x Ga _1-x ) _1-y In _y P used in the light emitting layers A1 to A3, the selectivity in the selective growth method during the formation of the light emitting layers A1 to A3 can be increased, and the light emitting layers A1 to A3 can be prevented from being formed on the masks M1 to M4.

At this time, the supply amount of the raw material for epitaxial growth is adjusted so that the Al composition ratio x is highest in the n-type cladding layer N, followed by the guide layers A1A-A3A, A1C-A3C or the barrier layer, and then the quantum well layer, in that order. For example, the compositions of the guide layers A1A-A3A, A1C-A3C and the barrier layer can be x=0.7, y=0.5, and the quantum well layer can have a smaller Al composition ratio x. The quantum well layer can be made of GaInP with an Al composition ratio x=0. The guide layers A1A-A3A, A1C-A3C and the active layers A1B-A3B function as core layers in the optical waveguide. The thickness of this core layer depends on the oscillation wavelength and the refractive index of each layer, but is approximately 50 nm to 500 nm in the case of a red laser, and can be set to about 100 nm, for example.

Here, the height position of the interface between the insulating layer M and the n-type cladding layer N can be made equal to the height position of the interface between each of the light-emitting layers A1 to A3 and the n-type cladding layer N. Therefore, after forming openings V1 to V3 with different opening widths in the insulating layer M on the n-type cladding layer N, the light-emitting layers A1 to A3 can be formed on the n-type cladding layer N.

Next, as shown in FIG. 2C, by using epitaxial growth, p-type cladding layers B1 to B3 and a cap layer (not shown) are sequentially formed on each of the light-emitting layers A1 to A3. Here, by increasing the Al composition x when the p-type cladding layers B1 to B3 are composed of (Al _x Ga _1-x ) _1-y In _y P, the selectivity in the selective growth method during the formation of the p-type cladding layers B1 to B3 can be reduced. This makes it possible to uniformize the film thickness of the p-type cladding layers B1 to B3. Furthermore, the polycrystalline semiconductor layer P is deposited on the insulating layer M, and the composition of the p-type cladding layers B1 to B3 can be uniformized. For example, the Al composition x can be set to 0.95. Al is more easily deposited on the masks M1 to M4 than Ga and In. In addition, once deposition of polycrystalline semiconductor occurs on the masks M1 to M4, deposition of Ga and In other than Al is also promoted, so that differences in film thickness and composition of the p-type cladding layers B1 to B3 due to patterns such as the opening widths of the openings V1 to V3 and the mask widths of the masks M1 to M4 are unlikely to occur. In addition, the polycrystalline semiconductor layer P has a higher resistance than the p-type cladding layers B1 to B3, so that grooves for electrically isolating the p-type cladding layers B1 to B3 can be omitted.

Next, as shown in FIG. 2D, the p-type cladding layers B1 to B3 are patterned by using photolithography and etching techniques to form ridges G1 to G3 in each of the p-type cladding layers B1 to B3. When forming the ridges G1 to G3 in each of the p-type cladding layers B1 to B3, banks T1 to T3 may be formed in each of the p-type cladding layers B1 to B3. Each of the banks T1 to T3 can be provided on both sides of each of the ridges G1 to G3. Each of the banks T1 to T3 can protect each of the ridges G1 to G3 from impacts applied to each of the ridges G1 to G3. Here, by providing the etch stop layers B1B to B3B in FIG. 1 in the p-type cladding layers B1 to B3, the etching in the depth direction of the p-type cladding layers B1 to B3 during the formation of the ridges G1 to G3 and the banks T1 to T3 can be stopped at the positions of the etch stop layers B1B to B3B.

Next, as shown in FIG. 2E, an insulating film Y made of a SiO ₂ film or the like is formed on the surfaces of the ridges G1 to G3, the banks T1 to T3 and the polycrystalline semiconductor layer P by a method such as plasma CVD.
Next, the insulating film Y is patterned using photolithography and dry etching techniques to form openings K1 to K3 in the insulating film Y that expose the upper surfaces of the ridges G1 to G3.

Next, as shown in FIG. 2F, an electrode material made of a metal such as Au is formed on the insulating film Y by using a method such as sputtering or vapor deposition.
Next, the electrode material on the insulating film Y is patterned by using photolithography and dry etching techniques to form the electrodes D1 to D3 connected to the ridges G1 to G3 through the openings K1 to K3. The electrodes D1 to D3 other than the portions connected to the ridges G1 to G3 are formed on the insulating layer 5. At this time, the electrodes D1 to D3 are formed on at least one of the banks in addition to the upper portions of the ridges G1 to G3, so that the impact applied to the ridges G1 to G3 during mounting can be weakened and protected. Furthermore, the compound semiconductor substrate S on which the electrodes D1 to D3 have been formed is cleaved into a bar shape. Then, by a method such as sputtering, an end face protection film is formed on the cleavage planes that become the end faces of the light emitting layers A1 to A3, and the bars with the end face protection film formed on the cleavage planes are divided into individual pieces to form the semiconductor laser Z1.

In the above embodiment, the method of forming the masks M1 to M4 on the n-type cladding layer N after the n-type cladding layer N is formed has been described. However, the masks M1 to M4 may be formed on the guide layer below the active layer after the n-type cladding layer N and the guide layer below the active layer are formed.

In the red laser, an AlGaInP active layer and an AlGaInP mixed crystal cladding layer are formed on a GaAs substrate, and the lattice constant of these crystals depends greatly on the composition ratio of the group III elements Al, Ga, and In. For this reason, if the selectivity of the selective growth method is high when forming the p-type cladding layers B1 to B3, it is difficult to establish lattice matching conditions for the p-type cladding layers B1 to B3 on each of the light-emitting layers A1 to A3.

At this time, near the active layers A1B, A2B, and A3B in FIG. 1, the composition is changed between the active layers A1B, A2B, and A3B by crystal growth with high selectivity in the selective growth method, while the supply of Al is increased during the deposition of the p-type cladding layers B1 to B3, thereby reducing the selectivity in the selective growth method, thereby making the composition uniform regardless of the size of the p-type cladding layers B1 to B3. As a result, the lattice mismatch with the GaAs substrate is suppressed for the p-type cladding layers B1 to B3 on each of the light-emitting layers A1 to A3, and crystals with fewer dislocations can be deposited. In addition, by reducing the selectivity in the selective growth method during the deposition of the p-type cladding layers B1 to B3, polycrystalline semiconductor layers P made of the same constituent elements as the p-type cladding layers B1 to B3 can be deposited on the masks M1 to M4. When the surfaces of masks M1 to M4 are covered with polycrystalline semiconductor layer P, selective growth is inhibited regardless of the composition of the raw material for epitaxial growth, and the raw material adheres to the entire surface of the wafer from which the laser chips are cut out.

Therefore, the selective growth of the GaAs cap layer formed after the p-type cladding layers B1 to B3 is inhibited, and the layer is formed over the entire surface of the wafer. However, in the mask region, the base is not a semiconductor crystal but a dielectric material such as _SiO2 or SiN, and has low conductivity, so that the polycrystalline semiconductor layer P can have the effect of electrically isolating adjacent emitters.

In the communication wavelength band of 1 to 1.6 μm, AlGaInAs or GaInAsP is used as the light-emitting layer material, and InP is used as the cladding layer material, which is deposited on an InP substrate. In this material system, the cladding layer is not a mixed crystal but is a single crystal InP, so thick crystal growth is possible while satisfying the lattice matching conditions between the light-emitting layer and the cladding layer.

In the infrared wavelength band of approximately 850 nm to 1000 nm, InGaAs, GaAs, or AlGaAs with a low Al composition is used as the light-emitting layer material, and AlGaAs with a relatively high Al composition is used as the cladding layer material, which is deposited on a GaAs substrate. The lattice constant of the AlGaAs in the cladding layer is hardly affected by the composition ratio of Al and Ga, so even if the composition ratio changes due to selective growth, the lattice mismatch is small, and it is possible to grow a thick film with few dislocations.

Third Embodiment
3A to 3G are cross-sectional views showing an example of a method for manufacturing a semiconductor light-emitting device according to the third embodiment. Note that Fig. 3A to 3G show views corresponding to a cross section taken along line DA-DA in the semiconductor laser Z0 shown in Fig. 1 as Example 1.

The manufacturing method of the third embodiment is similar to the manufacturing method of the second embodiment, except that the step of FIG. 3B is added to the manufacturing method of the second embodiment.
3B, the n-type cladding layer N is etched through the openings V1 to V3 formed in the insulating layer M on the n-type cladding layer N, thereby forming recesses H1 to H3 located in the partition regions E1 to E3 in the n-type cladding layer N. The depth of the recesses H1 to H3 can be set to be approximately the same as the film thickness of the light-emitting layer A1, and can be set to, for example, 100 nm. In order to mitigate etching damage, the depth of the recesses H1 to H3 may be made shallow, to about several nm.
After the step of Fig. 3B, the steps of Fig. 3C to Fig. 3G are carried out in the same manner as the steps of Fig. 2B to Fig. 2F to form the semiconductor laser Z2. Note that some or all of the guide layers A1A to A3A, the quantum well and barrier layers, and the guide layers 1C to A3C shown in Fig. 1 may be located below the masks M1 to M4 in the third embodiment.

At this time, each of the light-emitting layers A1 to A3 can be formed on the etched surface of the n-type cladding layer N, and the height position of the interface between the insulating layer M and the n-type cladding layer N can be made higher than the height position of the interface between each of the light-emitting layers A1 to A3 and the n-type cladding layer N. Therefore, after removing contaminants or defects on the surface of the n-type cladding layer N exposed at the openings V1 to V3, the light-emitting layers A1 to A3 can be formed on the n-type cladding layer N, and the crystal quality of the light-emitting layers A1 to A3 can be improved.

In order to improve the cleanliness of the surface of the n-type cladding layer N exposed to the openings V1 to V3 before the formation of the light-emitting layers A1 to A3, the surface of the n-type cladding layer N may be cleaned by irradiating it with ultraviolet light or the like, and the light-emitting layers A1 to A3 may be formed on this cleaned surface.

Fourth Embodiment
4A to 4G are cross-sectional views showing an example of a method for manufacturing a semiconductor light-emitting device according to the fourth embodiment. Note that Fig. 4A to Fig. 4G show views corresponding to a cross section taken along line DA-DA in the semiconductor laser Z0 shown in Fig. 1 as Example 1.

The manufacturing method of the fourth embodiment is similar to the manufacturing method of the second embodiment, except that the step of FIG. 4B is added to the manufacturing method of the second embodiment.
4B, the n-type cladding layer N is regrown on the openings V1 to V3 formed in the insulating layer M on the n-type cladding layer N, and the n-type cladding layer N is raised at the positions of the partition regions E1 to E3. The height of this raising can be set to approximately the same as the film thickness of the light-emitting layer A1, and can be set to 100 nm, for example. In order to suppress variations in the composition during the raising, the height of the raising may be reduced to approximately several nm.
After the step of Fig. 4B, the steps of Fig. 4C to Fig. 4G are carried out in the same manner as the steps of Fig. 2B to Fig. 2F to form a semiconductor laser Z3. Note that some or all of the guide layers A1A to A3A, the quantum well and barrier layers, and the guide layers 1C to A3C shown in Fig. 1 may be located above the masks M1 to M4 in the fourth embodiment.

At this time, each of the light-emitting layers A1 to A3 can be formed on the regrowth surfaces U1 to U3 of the n-type cladding layer N. The height position of the interface between the insulating layer M and the n-type cladding layer N can be lower than the height position of the interface between each of the light-emitting layers A1 to A3 and the n-type cladding layer N. An n-type cladding layer (regrowth surfaces U1 to U3) is additionally laminated on the openings V1 to V3 that have been affected by contamination due to exposure to the atmosphere by a thickness equivalent to this height difference. This makes it possible to prevent the light-emitting layers A1 to A3 from contacting the surface of the n-type cladding layer N that has been contaminated, etc., and the light-emitting layers A1 to A3 can be formed on clean surfaces (regrowth surfaces U1 to U3) that have been additionally laminated and are not affected by contamination, etc., thereby improving the crystal quality of the light-emitting layers.

In the above-described embodiment, an n-type clad layer is used as the first conductive type clad layer, and a p-type clad layer is used as the second conductive type clad layer. However, a p-type clad layer may be used as the first conductive type clad layer, and an n-type clad layer may be used as the second conductive type clad layer.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-mentioned embodiments and includes various modified examples. For example, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations.

Z0, Z1, Z2, Z3 Semiconductor lasers E1 to E3 Partition region N n-type cladding layers A1 to A3 Light-emitting layers B1 to B3 p-type cladding layers G1 to G3 Ridge M Insulating layer P Polycrystalline semiconductor layer

Claims (10)

a first conductivity type cladding layer;
an insulating layer that partitions the first conductive type clad layer;
m (m is an integer of 2 or more) light emitting layers each of which is laminated on the first conductive type clad layer partitioned by the insulating layer and emits laser light of different wavelengths;
m second conductive type clad layers respectively stacked on the m light emitting layers;
a polycrystalline semiconductor layer laminated on the insulating layer. The semiconductor light-emitting device according to claim 1, characterized in that the polycrystalline semiconductor layer contains the constituent elements of the second conductive type cladding layer as a main component. 3. The semiconductor light emitting element according to claim 1, wherein the light emitting layer contains ( _{AlxGa1 -x} ) _{1- yInyP} (0≦x<1, 0<y<1). 4. The semiconductor light emitting device according to claim 3, wherein the second conductive type cladding layer is made of ( _{AlxGa1 -x} ) _{1- yInyP} (0<x≦1, 0<y<1). 5. The semiconductor light emitting device according to claim 4, wherein a difference in Al composition x between the (Al _x Ga _1-x ) _1-y In _y P used in each of the m second conductive type cladding layers is smaller than a difference in Al composition x between the (Al _x Ga _1-x ) _1-y In _y P used in each of the m light emitting layers. The semiconductor light-emitting device according to claim 1 or 2, characterized in that the widths of the m light-emitting layers on the first conductive cladding layer partitioned by the insulating layer are different from each other. The semiconductor light-emitting element according to claim 1 or 2, characterized in that the insulating layer contains at least one oxide, nitride, or mixture of Si, Mg, Al, Hf, Nb, Zr, Sc, Ta, Ga, Zn, Y, B, and Ti. forming a first conductivity type cladding layer on a compound semiconductor substrate;
forming a mask having m (m is an integer of 2 or more) openings with different opening widths on the first conductivity type cladding layer;
selectively growing a light emitting layer on the first conductive type cladding layer located in the opening;
and laminating a second conductive type cladding layer on the light emitting layer while depositing a polycrystalline semiconductor layer on the mask. The method further includes a step of etching or cleaning the first conductive type cladding layer located in the opening,
9. The method for manufacturing a semiconductor light emitting device according to claim 8, wherein the light emitting layer is selectively grown on the etched surface or the cleaned surface of the first conductive type cladding layer. further comprising the step of regrowing the first conductivity type cladding layer in the opening;
9. The method for manufacturing a semiconductor light emitting device according to claim 8, wherein the light emitting layer is selectively grown on a regrown surface of the first conductive type cladding layer.

Images