JPH0736461B2 - Method of manufacturing semiconductor laser device - Google Patents

Description

The present invention relates to a method for manufacturing a distributed constant feedback type semiconductor laser device having a diffraction grating structure.

<Prior Art> Manufacturing methods of semiconductor laser devices are roughly classified into three types, that is, a Fabry-Perot resonance type, a distributed constant feedback type, and a Bragg reflection type, depending on the oscillation method. Among these semiconductor laser devices, the distributed constant feedback type and the Bragg reflection type have features such as stable dynamic single-mode operation and a small temperature coefficient of the oscillation wavelength, but it is necessary to form a diffraction grating for reflection. There is
The manufacturing process is more complicated than the Fabry-Perot resonance type.

FIG. 5 is a schematic view of a method of manufacturing a known distributed constant feedback type semiconductor laser device, in which a light bleeding layer 2 is provided on one side (upper side in FIG. 5) of an active layer 1 for laser oscillation. The diffraction grating 3 is sandwiched between them, and the light exuding into the light exuding layer 2 (ultra-high speed generated by the energy emitted when the electrons supplied to the active layer 1 transit from the conduction band to the valence band) Electromagnetic waves having a wave number) are periodically reflected by the diffraction grating 3 to become standing waves and oscillate. When the oscillation wavelength is λ and the refractive index is n, the period (pitch) d of the diffraction grating to be formed is (Where m is a constant, usually 1 or 3
Is).

In the method of manufacturing a semiconductor laser device described above, the oscillation wavelength λ
Is usually less than 1.5 μm and 0.85 for GaAs laser devices.
It is about μm. Therefore, when the refractive index n is 3.5, the pitch d of the diffraction grating is 0.12 μm in the first order (m = 1) and the third order (m =
Even in 3), it is a very small value of about 0.36 μm.

<Problems to be Solved by the Invention> It is difficult to form a fine diffraction grating pattern as described above by an ordinary photolithography method, and a mask is formed by a photoresist using the interference of laser light to form a semiconductor surface. Although it was etched to form unevenness to form a diffraction grating, the process was complicated and required high technology, resulting in poor reproducibility. Furthermore, when a semiconductor layer is grown on the formed diffraction grating, the diffraction grating may be deformed during the growth.

Further, since it is necessary to supply electrons to the active layer, good electrical insulation from other electronic devices can be obtained when the method of manufacturing a semiconductor laser device is formed on the same substrate as other electronic devices. As a result, high integration of opto-electronic devices has not been realized.

Therefore, it is desired to develop a method for manufacturing a semiconductor laser device, which can easily form a fine diffraction grating with high reproducibility in the method for manufacturing a semiconductor laser device and can be formed on the same substrate as other electronic devices. ing.

<Means for Solving the Problems> The present invention has been proposed in view of the above, and in a method for manufacturing a semiconductor laser device having a diffraction grating on one side of an active layer, a superlattice structure region and the superlattice structure region are provided. The above-mentioned diffraction grating is formed by the first non-superlattice structure region formed by the first impurity ion implantation into the above, and the second non-superlattice structure region is formed by performing the second impurity ion implantation on both sides of the diffraction grating. Then, the diffraction grating is formed in a stripe shape, and a high-concentration impurity implantation region is formed by implanting a third impurity ion at a high concentration to the side of the stripe-shaped diffraction grating, and the stripe-shaped diffraction grating is formed. , A semiconductor layer is crystal-grown on the surface of the superlattice layer, which is composed of the non-superlattice structure region and the high-concentration impurity implantation region, on the impurity ion implantation side, and the defect layer generated in the semiconductor layer is removed by etching In that in order to form an electrically insulating region Te.

<Operation> By injecting the first and second impurity ions as a focused ion beam into the superlattice structure region to form the first and second non-superlattice structure regions, it is possible to reduce the size The diffraction grating can be formed with high reproducibility.

By implanting the third impurity ions as a focused ion beam into the superlattice structure region, a defect layer is generated in the semiconductor layer crystal-grown on the surface of the superlattice layer on the impurity ion implantation side,
The defect layer can be easily removed by etching as compared with other crystal layers, and functions as an electrically insulating region.

<Example> Next, an example of the present invention will be described in detail with reference to the accompanying drawings.

1 and 2 show a method of manufacturing a GaAs-based distributed constant feedback semiconductor laser device manufactured by the present invention. For example, an n-type is provided on a substrate 4 made of n ⁺ -type GaAs.
A clad layer 6 made of n-type GaAs is provided below the buffer layer 5 made of GaAs, and an active layer 1 for emitting light is provided thereon. The active layer 1 may have an AlGaAs layer, a single-layer quantum well structure composed of two kinds of semiconductor ultrathin films having different compositions of GaAs and AlGaAs (or AlAs), or a multilayer quantum well structure in which a large number of layers are alternately stacked.

On the active layer 1, there is a light seepage layer 3 made of p-type AlGaAs, and on top of that, for example, 100 angstrom thick GaAs.
Layer, and a p-type superlattice layer 7, p-type AlGaAs layer 8 and p ⁺ GaAs layer 9 in which Be is added as a p-type impurity in a multilayer structure of an AlGaAs layer having a thickness of 100 Å, for example, are formed in order on the uppermost layer and Electrodes 13 and 14 are provided on the bottom surface of the substrate, respectively.

As shown in FIG. 2, the superlattice layer 7 includes a superlattice structure region 10 provided at a predetermined interval in the central portion, and a p-type impurity of the superlattice layer 7 except for the superlattice structure region 10. The n-type first non-superlattice structure region 11 into which Si ions having the above concentrations are implanted
And a second non-superlattice structure region 11 '. The impurities for forming the first and second non-superlattice structure regions 11 and 11 'are preferably atoms forming a conductivity type different from that of the superlattice structure, but may be impurities forming the same conductivity type. When impurities that form the same conductivity type are used, the current confinement in the superlattice structure depends only on the difference in the composition of each region of the superlattice structure and the non-superlattice structure, as described below. This is advantageous because the current can be confined by the pn junction.

The superlattice structure region 10 in the central region of the superlattice layer 7 and the first
The diffraction grating structure is formed in a stripe shape by the non-superlattice structure region 11, and more specifically, impurities are added to the superlattice layer at a predetermined interval (d = m · λ / 2n) in the direction perpendicular to the oscillation direction. Ion implantation is performed, and the superlattice structure is destroyed by heat treatment to form a non-superlattice mixed crystal region having a smaller refractive index than the superlattice structure, thereby forming an effective diffraction grating. Since the above-mentioned impurity ion implantation can be performed by a focused ion beam whose diameter is controlled on the order of submicron, it is possible to perform the impurity ion implantation accurately even when the above-mentioned interval is on the order of submicron. it can. Therefore, it is possible to easily form a fine diffraction grating with high reproducibility in the method of manufacturing a semiconductor laser device.

The second non-superlattice structure regions 11 '(non-superlattice formed by implantation of impurity ions) on both sides except the central region of the superlattice layer 7 acting as the diffraction grating have a lateral confinement function for electricity and light. .

Further, ions such as Si and Be of 10 ¹⁴ / c are provided as third impurity ions on both sides of the second non-superlattice structure region 11 ′, for example.
A high-concentration impurity-implanted region 12 injected at a high concentration of m ² or more is formed parallel to the diffraction grating in the laser oscillation direction, and then p
When the type AlGaAs layer 8 and the p ⁺ type GaAs layer 9 are crystal-grown, a defect layer 15 such as a polycrystalline layer is formed on the high concentration impurity implantation region 12, and the defect layer 15 is removed by etching. By doing so, it is electrically separated from the electronic device formed in the adjacent region. Therefore, even if the manufacturing method of the semiconductor laser device and the other electronic device are formed on the same substrate, good electrical insulation can be achieved, and high integration of the opto-electronic device can be realized. Become.

In the above description, the method of manufacturing a GaAs-based semiconductor laser device has been described, but similar effects can be expected not only in the GaAs-based method but also in other compound semiconductor laser device manufacturing methods.

When a current is supplied to the electrodes 13 and 14 of the method for manufacturing the semiconductor laser device manufactured by the above method, the holes injected from the electrode 13 and the electrons injected from the electrode 14 are combined in the active layer 1 to emit light. To do. Of the emitted light, the light that exudes to the light exuding layer 3 provided on one side (upper side in the drawing) of the active layer 1 is reflected by the stripe-shaped diffraction grating,
A standing wave is formed and an oscillation phenomenon occurs.

At this time, as in the semiconductor laser device manufactured by the present invention, the conductivity type of the superlattice layer 7 forming the diffraction grating is p-type, and the non-superlattice structure region is n-type with an AlGaAs crystal in which GaAs and AlGaAs are mixed. If so, the holes injected from the electrode 13 will not pass through the non-superlattice structure region but only through the superlattice region. Therefore, assuming that the pitch d of the non-superlattice structure region is λ / 2n, in the diffraction grating including the superlattice structure region and the non-superlattice structure region, the refractive index of the non-superlattice structure region is greater than the refractive index of the superlattice structure region. Therefore, a standing wave is formed with nodes near the non-superlattice structure region as nodes.

At this time, the current flows only in the superlattice structure region as described above, and the light exuding layer 3 below this superlattice structure region is a region in which the electric field strength of the standing wave is strong, so that the gain is increased and the oscillation efficiency is increased. Is improved.

Since the superlattice layer 7 is formed by repeating GaAs and AlGaAs, the difference in the forbidden band width between GaAs and AlGaAs serves as a potential barrier for flowing electrons or holes. If the band width difference is made small, the difference with the superlattice structure region becomes small when mixed crystals are formed by ion implantation of impurities, which is disadvantageous in confining light. The potential barrier of the GaAs-AlGaAs superlattice is said to be as large as the electron barrier is about five times the hole barrier. Therefore, it is advantageous that the superlattice structure region is an n-type having a small potential barrier rather than an n-type having a large potential barrier, because the resistance is reduced.

Next, one embodiment of a method of manufacturing the above-mentioned GaAs-based distributed constant feedback type semiconductor laser device will be described with reference to FIG.

Substrate 4 n-type impurity 5 × 10 on ¹⁷ / cm ³ consisting of the added buffer layer 5 made of GaAs, the n-type impurity 5 × 10 ¹⁷ / cm ³ is added to the Al _0.35 Ga _0.65 As clad layer 6,0.1μm Thick active layer 1 made of GaAs, p-type impurities 5 × 10 ¹⁷ / cm ³
0.6 μm thick Al _0.15 Ga _0.85 As doped light-exuding layer 3, p-type GaAs (100 μm) doped with impurities of 2 × 10 ¹⁷ / cm ³
20 Angstrom thick) -Al _0.4 Ga _0.6 As (100 Angstrom thick) superlattice layers 7 are sequentially grown by the molecular beam crystal growth method (FIG. 3A).

Next, the beam diameter is 0.1μ under high vacuum of 10 ^-10 Torr or more.
Without using a mask with an ion beam focused on m
Si is injected into the superlattice layer 7 at a concentration of 6 × 10 ¹³ / cm ² with an acceleration energy of 100 KeV at a predetermined interval (FIG. 3 (b)). The pitch of this first non-superlattice structure region 16 is 0.36
If the thickness is μm, a third-order diffraction grating will be obtained.
Further, similarly, impurities are left in the center of the diffraction grating in a stripe shape, and Si is injected into the both sides of the diffraction grating by an ion beam to form a second non-superlattice structure region 17 (see FIG. 3 (c). )). As a result, the current and light in the lateral direction are confined by the second non-superlattice structure region 17.

Further, in order to electrically separate the formed semiconductor laser device manufacturing method from other devices formed on the same substrate, Si at a high concentration of 10 ¹⁴ / cm ² or more at the boundary position on the substrate, High concentration impurity implantation region 12 by implanting impurities such as Be
Are formed (FIG. 3 (d)). The above-described implantation of impurity ions by the focused ion beam can be continuously performed without using a mask. Further, it is also easy to form a part having a different pitch for phase adjustment when forming the diffraction grating.

As described above, if the first to third impurity ions are implanted into the superlattice layer 7 to form the first non-superlattice structure region 11, the second non-superlattice structure region 11 ′, and the high-concentration impurity implantation region 12. , 5 × impurities on the surface of the superlattice layer 7 on the impurity injection side (upper surface in the figure).
10 ¹⁷ / cm ² the added p-type p-type AlGaAs layer 8 made of AlGaAs, impurities consisting of the 1 × 10 ¹⁹ / cm ² the added p-type GaAs P
^{The +} -type GaAs layer 9 is continuously crystal-grown under high vacuum, and finally a metal is vapor-deposited on the uppermost layer to form the electrode 13 (FIG. 3 (e)). In order to activate the impurities or to make the impurity-implanted portion non-superlattice, an annealing treatment is performed at 800 ° C. for about 30 minutes before forming the electrodes.

Further, in the p-type AlGaAs layer 8 and the P ⁺ -type GaAs layer 9 which are crystal-grown on the superlattice layer 7, the portion grown on the high-concentration impurity implantation region 12 is a defect layer 15 such as a polycrystal, H ₂ SO ₄ -
Since the etching rate of H ₂ O ₂ -H ₂ O-based aqueous solution is faster than that of a normal crystal layer, it can be easily distinguished from other regions by etching, and functions as an electrically insulating region. Therefore, it can be easily electrically separated from the device formed on the adjacent substrate.

As one example thereof, FIG. 4 shows two devices formed on a single substrate 4. A high-concentration impurity implantation region 12 is provided at the boundary between the laser device forming region 18 and the electronic device forming region 19. , After further crystal growth, a device is formed in each region, and thereafter, the defect layer 15 such as a crystal region grown on the high-concentration impurity implantation region 12 is removed by etching, whereby both devices are electrically connected. Will be separated. When it is desirable to form the P ⁺ -type GaAs layer 9 as an n-type or high-resistance GaAs layer, an AlGaAs layer, or a combination of these layers in order to form another device, the electrode 13 of the formed layer is provided. It suffices to diffuse zinc into the lower part of the position where it is made conductive.

In the illustrated embodiment, the high-concentration impurity-implanted regions 12 are formed on both sides of the diffraction grating. However, when an electronic device is provided only on one side, the high-concentration impurity-implanted region 12 is provided only on the side on which the electronic device is provided. The impurity-implanted region 12 may be formed. Further, the thickness or the number of layers of GaAs and AlGaAs forming the superlattice layer are not limited to those in the above embodiment.

<Effects of the Invention> As described above, according to the present invention, the diffraction grating structure, which has been troublesome to form until now, is formed in the superlattice structure region in the first and second regions.
Since it is formed by implanting the impurity ions of, it is possible to easily form a fine diffraction grating with high reproducibility. Also, the current flows only in the diffraction grating region,
The generated standing wave is affected, the gain is increased, and the oscillation efficiency is improved.

Furthermore, by injecting a third impurity ion at a high concentration to the side of the diffraction grating, a defect layer is generated in the semiconductor layer crystal-grown in the superlattice layer, and the defect layer is removed by etching. This allows good electrical insulation between another electronic device provided on the same substrate and the method for manufacturing the semiconductor laser device, which greatly contributes to high integration of the opto-electronic device.

[Brief description of drawings]

The drawings show one embodiment of the present invention. FIG. 1 is a perspective view of a method for manufacturing a semiconductor laser device manufactured by the present invention, and FIG. 2 is a perspective view of the laser device with a part cut away,
3 (a) to 3 (e) are views showing the outline of the manufacturing steps of the method for manufacturing a semiconductor laser device, FIG. 4 is a perspective view showing a state in which another electronic device is formed on the same substrate, and FIG. It is a perspective view of the manufacturing method of the conventional distributed constant feedback type semiconductor laser device. In the figure, 1 is an active layer, 7 is a superlattice layer, 8 is a p-type AlGaAs layer,
9 is a p ⁺ type GaAs layer, 10 is a superlattice structure region, 11 is a first non-superlattice structure region, 11 'is a second non-superlattice structure region, 12 is a high-concentration impurity implantation region, and 15 is a defect layer. .

 ─────────────────────────────────────────────────── --Continued from the front page Judgment body for referee Judge Masaaki Endo Judge Yoshihiro Samura Judge Akira Kawai (56) References JP60-7190 (JP, A) JP61-184894 (JP, A) )

Claims (1)

[Claims] 1. A method of manufacturing a semiconductor laser device having a diffraction grating on one side of an active layer, comprising: a superlattice structure region; and a first non-superlattice formed by first impurity ion implantation into the superlattice structure region. A step of forming the diffraction grating by the structural region, a second step on each side of the diffraction grating
Of the second non-superlattice structure region by implanting the impurity ion to form the diffraction grating in a stripe shape, and by implanting the third impurity ion at a high concentration to the side of the stripe-shaped diffraction grating, A step of forming a high-concentration impurity-implanted region, a step of crystal-growing a semiconductor on the surface of the superlattice layer including the stripe-shaped diffraction grating, the non-superlattice structure region and the high-concentration impurity-implanted region on the impurity ion-implanted side, A method of manufacturing a semiconductor laser device, comprising the step of removing a defective layer formed in a layer by etching to form an electrically insulating region.