JPS622719B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a semiconductor laser device,
More specifically, the present invention relates to an element in which functional circuit elements for modulating the current flowing through a light emitting region are integrated, and a method for manufacturing a semiconductor laser device including an integrated circuit.

Recently, there has been a demand for using semiconductor laser elements in combination with circuits to operate them as functional devices. For example, proposals have been made to combine a modulation circuit and a semiconductor laser element to emit laser light when the output of the circuit is a constant value, and to introduce it into a glass fiber or the like for application to optical communications.

Conventionally, in this type of device, a high resistivity or conductive semiconductor layer has been formed by a liquid phase growth method, a thermal diffusion method, or the like. However, in the liquid phase growth method described above, it is difficult to accurately control the doping amount, and it is difficult to form a stable high resistivity layer.
In addition, selective liquid phase growth has the disadvantage that the semiconductor layer is formed with mutual effects such as strain on other semiconductor layers, resulting in extremely electrical deterioration of the finished device. .

SUMMARY OF THE INVENTION An object of the present invention is to provide a novel method for manufacturing a semiconductor laser device that is free from the above-mentioned drawbacks, has a simple structure, and is suitable for using a semiconductor laser element in a functional device circuit or the like.

The structure of the present invention to achieve the above object includes a step of further forming a single layer or a multilayer semiconductor layer on an active layer provided on a semiconductor substrate, and selecting oxygen or Al element in the layer. and a step of providing a high resistivity layer formed by the ion implantation or a circuit element formation region on the layer.

In the present invention, by converting a semiconductor layer into a high resistivity layer by ion implantation as described above, a high resistivity layer with good interface and surface conditions and good electrical characteristics is formed. That is, unlike liquid phase growth methods, which are formed by successively stacking new layers, existing semiconductor layers are gradually converted into high resistivity layers one by one, so stable layers can be obtained without difficulty. Subsequently, an element formation region is formed in a later step. Since this step is carried out in a high temperature atmosphere of 800 to 1000° C., it is used in conjunction with a heat treatment step after substantial ion implantation, and has the advantage of simplifying the process. Implant energy is 800-1500KeV
It is driven at 10 ¹³ to 10 ¹⁵ cm ^-2 . This implantation energy is several times higher than when doping with normal conductivity type impurities. If it is less than 800 KeV, a sufficiently high resistivity layer cannot be obtained, and if it exceeds 1,500 KeV, it may even cause defects in the semiconductor layer, which is not preferable. Although the implantation depth varies depending on the desired size of the device, it is generally 1 to 5 μm, and it is important that the implantation depth is such that it does not reach the active layer and is deeper than the cap layer.

Further, it is necessary to perform the implantation selectively in advance through a predetermined mask to avoid the laser emission region. As mentioned above, since it is implanted with high energy, it is possible to easily form a high resistivity layer to a deep depth. Furthermore, the concentration of implanted atoms has a peak value at a distance of 0.5 to 0.6 μm from the surface. This has a region with a higher insulating effect inside a given semiconductor layer, making the high resistivity layer even more effective, and also causes crystalline damage due to large amounts of doping at the surface and deeper regions within the semiconductor layer. It is also used in combination with effects that can prevent this from occurring. These implantation techniques are extremely easy to use when forming regular silicon semiconductor devices because the same substrate is used and no new special accessory equipment is required. A semiconductor laser with good quality can be provided.

In this way, ion implantation forms a high resistivity layer while keeping the implanted semiconductor layer extremely crystalline and stable without destroying it, so it is possible to implant other semiconductor elements into this implanted layer. This makes it possible to form an element formation region. In addition, since this implanted layer is obtained with a stable surface, the crystal consistency is good, and even if another semiconductor layer is formed on the implanted layer, this semiconductor layer will have perfect crystallinity. This makes it possible to use the area as an element forming area.

As mentioned above, by forming a high resistivity layer that is very close to an insulator in the semiconductor layer, the light emitting element portion such as a laser and the circuit portion are separated.
They are connected by a wiring layer. For this reason, since the high resistivity layer is selectively provided, the current from the electrode is concentrated in a specific region, which has a current confinement effect in the laser element, promoting efficiency of the operating current, and improving the efficiency of the laser element. Insulate and separate from active circuits. This insulation isolation is achieved by ion implantation of an element different from conductivity type impurities into the semiconductor layer to form a high resistivity layer. Since the capacitance is extremely small, high frequency characteristics are good. This high resistivity layer is formed by implanting oxygen ions or the like into a compound semiconductor layer such as GaAs or GaAlAs by ion implantation. In addition to the above-mentioned oxygen and Al, other ion sources may be used depending on the purpose as long as they do not change after implantation, but it is important that the resistivity does not become low due to heat treatment after implantation. In this sense, oxygen, Al, etc. are preferable. The high resistivity layer may have a depth that is shallower than the active layer of the laser and deeper than the cladding layer, although it is sufficient that the laser element portion and the circuit element portion are separated as described above. In this way, the operating current can be used more effectively without spreading before it reaches the active layer, and the effect of current narrowing can be further enhanced without deterioration of crystallinity due to implantation affecting the active layer.
In addition, semiconductor materials include In, Ga, Al,
It is important that the constituent elements be at least three of the group consisting of AsP and Sb. This is because these are extremely effective for semiconductor lasers having a heterojunction. This will be explained in detail below using examples.

Example 1 FIG. 1 is a schematic cross-sectional view of a semiconductor laser device of the present invention. A cross-sectional view taken in a plane perpendicular to the traveling direction of laser light is shown.

On the n-GaAs substrate 1, a layer of n-Ga _1-x Al _x As (0.2≦x
≦0.7), and an active layer 2 formed on the layer 2 of n-type or p-type or undoped Ga _1-y Al _y As (0≦y≦0.3) with a thickness of 0.05 to 1.5 μm. layer 3 and a p- layer with a thickness of 1 to 3 μm on the layer 3;
A second cladding layer 4 made of Ga _1-z Al _z As (0.2≦z≦0.7), and a p-GaAs layer 4 with a thickness of 0.1 to 0.7 μm on the second cladding layer 4.
A cap layer 5 is formed. A high resistivity layer 6 is formed around this cap layer 5 by, for example, oxygen ion implantation. The width of the cap layer 5 is approximately 1.5 to 2.5 μm. In this way, a laser element with a narrow operating current is constructed. Note that a region 15 indicated by a broken line indicates an existing light emitting region of the laser. In order to control the transverse mode of the laser, a recess (groove) having an inverted trapezoidal cross section may be provided in advance in the substrate 1 as shown in the figure. An n-GaAs layer 7 forming a circuit element formation region is provided on the high resistivity layer 6 by a method described later, juxtaposed to the laser element region. The area 7
Circuit functional elements are formed on or in the region 7 by known manufacturing means. For example, as shown in the figure, a source electrode 8, a gate electrode 9, a drain electrode 10,
A field effect transistor is constructed by providing an insulating film 14 and metal electrodes 12 and 13. FIG. 2 is a schematic top view of FIG. 1 above. The metal wiring 12 is connected to the electrode section 11 of the laser. On the other hand, the source electrode 8 of the FET
It is connected to the. The gate electrode 9 is connected to a gate bonding pad 16 in the middle by dividing the electrode 13 connected to the drain electrode 10. The form and shape of these electrodes 12, 13, and 16 can be changed as appropriate depending on the circuit element and purpose of use. Next, the manufacturing method of the present invention will be described.

Each semiconductor layer 2, 3, 4 and 5 of the semiconductor laser
is easily formed on a predetermined semiconductor substrate by a liquid phase growth method using a conventional sliding method. For example, in the semiconductor layer 2, the composition of the crystal solution is Ga.
6g, 400mg GaAs, 10mg Al, and 0.5mg Te.
It can be obtained by adjusting. In addition, active layer 3
is 6g of Ga, 400mg of GaAs, and 2mg of Al.
In addition, cladding layer 4 contains 6 g of Ga, 400 mg of GaAs,
The cap layer 5 is obtained by adjusting Al to 10 mg and Zn to 30 mg. Furthermore, the cap layer 5 is obtained by adjusting Ga to 6 g, GaAs to 400 mg, and Zn to 30 mg.

As shown in Figure 3, striped grooves (depth
Semiconductor layers 2 to 5 as described above are grown on an n-type GaAs semiconductor substrate having a thickness of 0.5 to 5 μm) 18. The thickness of each layer is as described above.

An ion implantation mask 17 is formed in a band shape using photoresist or the like above the region where laser oscillation is to be performed (this corresponds to the above-mentioned groove portion).

As shown in FIG. 4, oxygen ions 21 are implanted at 800 KeV and at a depth of 0.5 to 2 μm through an ion implantation mask 17.
is implanted to form a high resistivity layer 6. Next, as shown in FIG. 5, after removing the mask 17, the n-
A GaAs layer 7 having a thickness of 0.2 to 5 μm is formed by liquid phase growth. By using a normal chemical etching method, the n-GaAs layer 7 is left only in the part where the FET will be formed. The p-GaAs layer 5 is exposed on the region corresponding to the laser element portion (FIG. 6). A SiO ₂ film 14 with a thickness of 0.5 μm is formed on the entire surface of the semiconductor substrate prepared in this way by the CVD method, and then a SiO 2 film 14 is formed at the locations corresponding to the source and drain.
Selectively remove the SiO ₂ film. FIG. 7 shows this state. Au--Ge--Ni is deposited on the removed portions, patterned into a predetermined shape, and then alloyed to form the electrodes 8, 10. Next, as shown in FIG. 1, the SiO ₂ film corresponding to the laser electrode part is opened, and the laser electrode part and the gate electrode part are opened.
A predetermined metal pattern is formed by depositing a layer of Ti, Gr, and Au. Polish the back side of the substrate crystal to 100μ
After thinning to about m, Au is used as the n-side electrode 18.
- After depositing Sn, separate the elements and perform bonding. In this way, a semiconductor laser device equipped with an active circuit is formed. Figure 1 shows this completed drawing.

Laser oscillation threshold current value is 60mA, maximum output
It was possible to modulate at 3GHz with 10mW.

The manufacturing method of the present invention can be improved. This example will be explained using FIGS. 8 and 9. In Figure 8, after laser structure creation, when oxygen ions are implanted, 800~
As shown on the right side of the figure, the oxygen concentration at the surface is relatively low, and the
A profile with a peak at 0.5-0.6 μm is formed. At this time, the oxygen concentration near the peak is sufficiently high that the laser and FET are completely separated.
In addition, the oxygen concentration near the surface is sufficiently low that the characteristics of the FET manufactured here are not impaired. Furthermore, as shown in Figure 9, if Si or Se is Si, then 75~
100KeV, 5×10 ¹¹ ~ 5×10 ¹² cm ^-2 Se is 250 ~
300KeV5×10 ¹¹ to 5×10 ¹² cm ⁻² An active layer 19 for forming an element such as an implanted FET is formed. At this time, Si or Se is implanted by selective ion implantation through a photoresist mask 20, and the FET and laser are implanted.
Alternatively, it is electrically isolated from other FETs. The subsequent gates and electrodes are formed by the same method as in FIG. 7 described above, so their explanation will be omitted.

Example 2 The present invention is based on the GaAs
-It can be applied to semiconductors other than GaAlAs-based semiconductors, and a semiconductor laser with excellent high-speed modulation characteristics can be obtained. In the following explanation, for convenience, FIG. 1 in the above embodiment will be used. This is because the functions, effects, etc. are exactly the same, only the constituent materials are different.

An n-type InP layer 2 (thickness 1 μm) is formed on the n-type InP substrate 1.
_m ), undoped _{In0.73Ga0.27As0.63P0.37} laser active _layer 3 ( _{thickness 0.1μm} ) _, p- _{type InP4} (thickness 1.5μm)
m) was prepared by a liquid phase growth method, oxygen ions were implanted at 1000 KeV, and a device was prepared in the same manner as in Example 1 above. In this case, the second cladding layer 4 and the cap layer 5 are the same. 7, n-type
An InP layer was used. Laser oscillates at a wavelength of 1.6μm,
It was possible to modulate at 2.5GHz.

Example 3 On n-type InP substrate 1, n-type In ₀ . ₅₂ Al ₀ . ₄₈ As layer 2
(thickness 1.0 μm), n-type _{In 0.53 Ga 0.47} As layer ₃ (thickness
0.12 μm), p _{-type In 0.52 Al 0.48} As layer ₄ (thickness 1.0 μm)
m) is grown by molecular beam epitaxial method in a high vacuum. Next, without taking the wafer out of vacuum, a pattern was selectively drawn with an oxygen ion beam to form the high resistivity region 6 shown in Example 1. This method allows pattern formation by direct ion implantation without using photoresist.

After the ion implantation, an n-type In _{0 . 53} Ga ₀ . The following is
Since it can be manufactured by the same method as in Example 1, the explanation will be omitted.

As detailed above, the present invention is characterized in that a high resistivity layer near the laser element is formed by high-energy ion implantation to electrically isolate the element from the circuit elements and to narrow the current. It is possible to provide a semiconductor laser device equipped with a compact integrated circuit with good electrical characteristics, which is of great industrial benefit.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of a semiconductor laser device formed using the present invention, FIG. 2 is a top view of FIG. 1,
3 to 7 are schematic partial process diagrams as an example of the present invention, and FIGS. 8 and 9 are schematic partial process diagrams as an example of the present invention. DESCRIPTION OF SYMBOLS 1... Substrate, 2... First cladding layer, 3... Active layer, 4... Second cladding layer, 5... Cap layer, 6... High specific resistance layer, 7... N-type FET active layer, 8... Source, 9... Gate, 10... Drain, 12 and 13... Conductive wiring layer, 14...
Insulating film, 15... light emitting region.

Claims (1)

[Scope of Claims] 1. A step of forming a plurality of semiconductor layers including an active layer for emitting laser light on a semiconductor substrate, and forming high resistivity regions at predetermined locations in the plurality of semiconductor layers by an ion implantation method. A method for manufacturing a semiconductor laser device, comprising the steps of: forming a semiconductor layer at least on the high resistivity region; and forming at least a circuit element in the semiconductor layer. 2. In claim 1, the impurity concentration in the high resistivity region formed by the ion implantation method is low at least on the surface side thereof;
A method for manufacturing a semiconductor laser device, characterized in that the impurity concentration distribution has an impurity concentration peak within the high resistivity region.