JP2868074B2 - Surface emitting device and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a surface-emitting element whose wavelength is precisely controlled and used for wavelength-division multiplexed light transmission, and a method of manufacturing the same.

[0002]

2. Description of the Related Art At present, light is emitted in a direction perpendicular to the substrate surface of a semiconductor substrate in order to apply the parallelism and spatial propagation properties of light to data links between boards and other optical information processing. Research on two-dimensional integration of the surface emitting element to be performed and research on the surface emitting element itself have been advanced.

Further, as research on such a surface emitting element progresses, an increase in parallel information processing capacity can be expected.

[0004] Pioneering research has been conducted by Iga et al. On such surface emitting semiconductor laser devices.
Their series of research achievements was published in the 1988 Journal of Quantum Electronics.
ntum Electronics), including a historical background, in a paper by Iga et al., Vol. 24, pp. 1845-1855.

[0005] In the case where such a surface light emitting element uses the wavelength of light as one piece of information in, for example, wavelength multiplexing optical transmission or the like, the wavelength of the surface light emitting element corresponding to the transmitting device needs to be precisely controlled. .

Conventionally, in order to control the wavelength of the surface emitting element, a method of precisely controlling the film pressure during crystal growth has been adopted. Therefore, a technique of monitoring the film pressure by reflection measurement or the like during crystal growth. Was commonly used.

[0007]

However, there is a problem that an expensive measuring instrument is required for the above-described monitor during the crystal growth.

In view of the above, the present invention has been made to solve the above-mentioned problems and to provide a simple and low-cost surface-emitting element whose wavelength is precisely controlled without using expensive measuring equipment and a method of manufacturing the same. Aim.

[0009]

The present invention provides the following means for solving the above-mentioned problems.

That is, according to the present invention, a semiconductor substrate of a first conductivity type, a first multilayer reflection film formed on the semiconductor substrate of the first conductivity type, and an upper portion of the first multilayer reflection film An intermediate layer including an active layer provided in the, and a second multilayer reflective film provided in the information of the intermediate layer, a surface emitting element that emits light in a direction perpendicular to the semiconductor substrate, Wavelength control made of a material whose lattice constant matches that of the material of the intermediate layer at least between the first multilayer reflective film and the intermediate layer and between at least one of the intermediate layer and the second multilayer reflective film. A surface-emitting device comprising a layer and having a wavelength controlled by changing the refractive index of the wavelength control layer by heat treatment.

Further, according to the present invention, there is provided a method for manufacturing a surface-emitting device which emits light in a direction perpendicular to a semiconductor substrate, wherein a semiconductor substrate of a first conductivity type is prepared, and a semiconductor substrate of the first conductivity type is provided. Forming a first multilayer reflective film of the first conductivity type on the first multilayer reflective film, a first clad layer of the first conductive type, an active layer, and a second clad layer of the second conductive type on the first multilayer reflective film Are sequentially formed, a wavelength control layer is formed on the second clad layer at a predetermined crystal growth temperature at which the refractive index of the wavelength control layer is uniquely determined, and the refractive index is uniquely determined in the forming step. The wavelength control layer is subjected to a heat treatment so as to have a refractive index necessary for controlling the wavelength to a desired wavelength, and forming a second multilayer reflective film on the wavelength control layer. As a result, a method for manufacturing a characteristic surface emitting element is obtained.

Further, according to the present invention, in the method for manufacturing a surface emitting device, after forming a wavelength control layer on the second cladding layer, the substrate temperature of the semiconductor substrate is maintained at room temperature, and reflection spectroscopy is performed. Perform the measurement, and compare the measured value reflection spectrum, which is the actual measurement value of the reflection spectrum obtained as a result of the reflection spectroscopy measurement, with the design value reflection spectrum, which is the reflection spectrum of the desired wavelength, to confirm the wavelength shift, With the refractive index of the wavelength control layer as a parameter, calculate to approach a desired wavelength, determine the optimal refractive index of the wavelength control layer, and adjust the refractive index of the wavelength control layer to the optimal refractive index. A method for manufacturing a surface-emitting element, comprising performing a heat treatment and forming a second multilayer reflective film on the wavelength control layer, is obtained.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

First, as a feature of the surface emitting element of the present invention, the first multilayer reflective film (reflective film on the semiconductor substrate side) formed on the semiconductor substrate and the first multilayer reflective film are formed above the first multilayer reflective film. At least one of between the intermediate layer (including the active layer) and between the second multilayer reflective film formed above the intermediate layer and the intermediate layer is made of a material whose lattice constant matches that of the material of the intermediate layer. It has a wavelength control layer.

Also, in the process of manufacturing such a surface light emitting device, it is possible to control the wavelength by forming a wavelength control layer and then performing a heat treatment to change the refractive index of the wavelength control layer.

In the present embodiment, a surface light emitting device in which a wavelength control layer is formed after forming an intermediate layer as shown in FIG. 1 is taken as an example, and the contents of the present invention are more specifically understood. As described above, as an example, a method for manufacturing a surface emitting element having an oscillation wavelength of 980 nm will be described in detail with reference to FIGS.

First, as an n-type semiconductor substrate 11, n-type Ga
An As substrate is prepared.

Next, on the n-type semiconductor substrate 11, an n-type AlAs layer and an n-type GaAs layer are
For example, 18 cycles are alternately laminated at a film pressure of 9.5 nm, thereby forming an n-type semiconductor multilayer film 12 (first multilayer reflection film).

Next, for example, an Al _0.25 Ga _0.75 As layer is formed on the n-type semiconductor multilayer film 12 as an n-type clad layer 13 (first conductive type first clad layer) to a thickness of 145.7 nm. The active layer 14 is formed on the n-type cladding layer 13.
For example, three layers of In _0.2 Ga _0.8 As are formed with a width of 10 nm. Further, a p-type cladding layer 15 is formed on the active layer 14.
As the (second cladding layer of the second conductivity type), for example, Al
_A 93.3 nm _0.25 Ga _0.75 As layer is formed.

Incidentally, the steps so far are usually performed at about 600 ° C.

After the formation of the p-type cladding layer 15, the substrate temperature is lowered to maintain the substrate temperature at 200 ° C., and the wavelength control layer 1 is formed on the p-type cladding layer 15 at the substrate temperature of 200 ° C.
6, a GaAs layer is formed to a thickness of 50 nm (FIG. 2).
(C)).

In the present embodiment, the wavelength control layer 16
The refractive index of GaAs or AlGaAs used as
When a crystal is grown at 0 ° C. to 300 ° C., the refractive index of the wavelength control layer 16 in this case (crystal growth at 200 ° C.) is also known.

Next, after the above steps, the substrate temperature is once lowered to room temperature, and reflection spectroscopy is performed.

Here, it is assumed that as a result of the reflection spectroscopy measurement, a waveform showing a resonance peak (a reflection spectrum of an actually measured value) as shown by a solid line in FIG. 3 is obtained.

The measured measured reflection spectrum is compared with a waveform (represented by a bar dotted line in FIG. 3; a reflection spectrum of a design value) showing a resonance peak and a stop band when the growth proceeds as designed, and the wavelength is compared. Check the gap.

Here, the wavelength control layer 16 is subjected to waveform fitting so that a design structure having a design value reflection spectrum is again obtained using the refractive index of the wavelength control layer 16 as a parameter, and the wavelength control layer 16 approaches the design value reflection spectrum. Is determined as the optimum refractive index. In the present embodiment,
As shown in FIG. 3, the optimum refractive index is determined to be 3.6.

When the optimum refractive index is determined, the heat treatment temperature at which the optimum refractive index is obtained is determined from the relationship between the refractive index and the heat treatment temperature as shown in FIG. 4, and annealing (heat treatment) is performed according to the heat treatment temperature. In the present embodiment, FIG.
Thus, the heat treatment temperature is determined to be 500 ° C., and the heat treatment is performed at 500 ° C. (FIG. 2B).

After the annealing, the reflection mirror 17 (second multilayer reflection film) is formed on the wavelength control layer 16 by, for example, SiO 2.
A dielectric mirror in which ₂ and Si are alternately stacked at 168 nm and 71 nm respectively is formed.

Then, to take the p-side electrode, the reflecting mirror 1
7 is etched in a mesa shape using buffered hydrofluoric acid or the like as shown in FIG. 2C, and an electrode (for example, Cr / Au) is deposited from above the etched reflecting mirror 17. Here, the electrode may be deposited on the etched reflector 17 as it is.

As described above, it is possible to provide a surface light emitting element whose wavelength is precisely controlled at a simple and low cost without using expensive measuring equipment.

In the present embodiment, the wavelength control layer 16 is formed on the p-type cladding layer 15, that is, on the intermediate layer including the active layer 14. The present invention is not limited to the present embodiment, as long as it is between the first multilayer reflective film and the second multilayer reflective film.

However, from the viewpoint of ease of manufacture and ease of finding the optimum refractive index of the wavelength control layer, a surface emitting device manufactured according to the manufacturing method described in the present embodiment is recommended.

In the present embodiment, when forming a GaAs layer as the wavelength control layer 16, the substrate temperature is set to 200 degrees.
C., but the substrate temperature is not limited to this embodiment as long as the substrate temperature is 200 ° C. or higher and 300 ° C. or lower.

In this embodiment, GaAs is used as the material of the wavelength control layer 16. However, since it is basically sufficient to match the lattice constant with the material of the intermediate layer including the active layer, for example, AlGaAs may be used. Such a ternary mixed crystal or a quaternary mixed crystal with matching lattice constant may be used, and is not limited to the present embodiment.

Further, in this embodiment, the oscillation wavelength of the surface light emitting device, the semiconductor material, the dielectric material, the electrode material, and the like used for producing the surface light emitting device are merely examples, and the present invention is not limited thereto. It is not limited to a form.

For example, an n-type GaAs substrate is used as a semiconductor substrate, and an n-type AlGaAs (x =
0.1) and n-type AlGaAs (x = 0.9), a multi-layer reflective film, n-type AlGaAs as the first cladding layer
A cladding layer, a GaAs active layer as an active layer, a p-type AlGaAs cladding layer as a second cladding layer, a wavelength control layer made of GaAs or AlGaAs as a wavelength control layer,
A multilayer reflective film made of SiO ₂ and Si may be used as the second multilayer reflective film.

Alternatively, an n-type InP substrate is used as a semiconductor substrate, and n-type GaInAsP and n are used as a first multilayer reflection film.
Multi-layer reflective film made of n-type InP, an n-type InP clad layer as a first clad layer, an active layer made of InGaAs and InGaAsP as an active layer, a p-type InP clad layer as a second clad layer, and GaAs or AlGaAs as a wavelength control layer And a multilayer reflective film made of SiO ₂ and Si may be used as the _second multilayer reflective film.

Alternatively, an n-type GaAs substrate is used as a semiconductor substrate, and n-type AlAs and n-type Ga
A multilayer reflective film made of As, an n-type InP clad layer as a first clad layer, an InGaAsP active layer as an active layer, a p-type InP clad layer as a second clad layer, and a wavelength control layer made of GaAs or AlGaAs as a wavelength control layer Alternatively, a multilayer reflective film made of SiO ₂ and Si may be used as the _second multilayer reflective film.

Alternatively, an n-type GaAs substrate is used as the semiconductor substrate, and n-type AlAs and n-type Ga are used as the first multilayer reflection film.
A multilayer reflective film made of As, an n-type InGaP clad layer as a first clad layer, an InGaAs active layer as an active layer, a p-type InGaP clad layer as a second clad layer, and a wavelength control layer made of GaAs or AlGaAs as a wavelength control layer And SiO ₂ and S as the second multilayer reflective film.
A multilayer reflective film made of i may be used.

In the examples described above, the second multilayer reflection film may be replaced with a multilayer reflection film made of MgO and Si.

Further, in this embodiment, an example of a method for determining the optimum refractive index of the wavelength control layer 16 is shown, but other methods may be used as long as the optimum refractive index can be obtained. Not limited to

[0042]

According to the present invention, it is possible to provide a surface light emitting element whose wavelength is precisely controlled at a simple and low cost without using expensive measuring equipment.

Further, according to the present invention, it is possible to provide the simplest method for manufacturing the above-mentioned surface light emitting device.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a surface emitting device according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view showing a method for manufacturing the surface light emitting device shown in FIG.

FIG. 3 is a diagram showing a reflection spectrum at an actually measured value, a design value, and an optimum refractive index in the embodiment of the present invention.

FIG. 4 is a diagram showing a heat treatment temperature and a change in refractive index in the embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 11 n-type semiconductor substrate 12 n-type semiconductor multilayer film 13 n-type clad layer 14 active layer 15 p-type clad layer 16 wavelength control layer 17 reflector

Claims (3)

(57) [Claims] A first conductive type semiconductor substrate; a first multilayer reflective film formed on the first conductive type semiconductor substrate; and an active layer provided above the first multilayer reflective film. And a second multilayer reflective film provided above the intermediate layer, wherein the surface emitting element emits light in a direction perpendicular to the semiconductor substrate. Between the film and the intermediate layer, and at least one between the intermediate layer and the second multilayer reflective film, the material of the intermediate layer and a material whose lattice constant matches,
A surface emitting device comprising a wavelength control layer whose refractive index is optimized by heat treatment so as to oscillate at a desired wavelength. 2. A method for manufacturing a surface-emitting device that emits light in a direction perpendicular to a semiconductor substrate, comprising: preparing a semiconductor substrate of a first conductivity type; and forming a semiconductor substrate of the first conductivity type on the semiconductor substrate of the first conductivity type. Forming a first multilayer reflective film, sequentially forming a first conductive type first clad layer, an active layer, and a second conductive type second clad layer on the first multilayer reflective film; A wavelength control layer is formed on the second cladding layer at a predetermined crystal growth temperature at which the refractive index of the wavelength control layer is uniquely determined. On the other hand, a surface light emitting device characterized in that a heat treatment is performed so as to have a refractive index necessary for controlling to a desired wavelength, and a second multilayer reflective film is formed on the wavelength control layer. Manufacturing method. 3. The method for manufacturing a surface light emitting device according to claim 2, wherein after forming a wavelength control layer on the second cladding layer, the substrate temperature of the semiconductor substrate is maintained at room temperature, and reflection spectroscopy is performed. And comparing the measured value reflection spectrum, which is the actual measurement value of the reflection spectrum obtained as a result of the reflection spectroscopy measurement, with the design value reflection spectrum, which is the reflection spectrum of the desired wavelength, to confirm the wavelength shift, Using the refractive index of the wavelength control layer as a parameter, calculation is performed so as to approach a desired wavelength, the optimum refractive index of the wavelength control layer is determined, and heat treatment is performed so that the refractive index of the wavelength control layer becomes the optimum refractive index. And forming a second multilayer reflective film on the wavelength control layer.