JPH01239984A - Semiconductor laser diode and its manufacture - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to striped laser diodes and surface emitting laser diode arrays mounted on optoelectronic integrated circuits (OEIG), which require a low threshold value and high yield. The present invention relates to a semiconductor laser diode and its manufacturing method.

[Conventional technology]

In order to lower the threshold voltage of a laser diode, it is necessary to use a buried structure. For example, the lowest threshold stripe laser diodes currently available are Y,
Applied PhysicsL by Lau et al.
etters-52, p.88 (1988).

This laser diode was manufactured through the following steps. First, GRIN-3CII (Graded
Refractive Index-3eparate
Confinement
ture)CM, Ge)As laser structure is grown by MBE method. Next, this sample is etched, leaving only the necessary portion, and is subsequently filled in by regrowth of GaAs.Finally, the end face is coated with a high reflectance dielectric multilayer film to complete the sample. With this structure, the threshold value is 0.551
Room temperature continuous oscillation of 1A was achieved.

[Problem to be solved by the invention]

When attempting to mount the above-mentioned laser diode on an 0EIC, a drawback is that regrowth is required for embedding. In a circuit that integrates many elements such as an 0EIC, a reduction in yield is a serious problem, and regrowth of the buried layer reduces this yield.

The same can be said of surface-emitting laser diode arrays; the current embedded type surface-emitting laser diodes are not suitable for surface-emitting laser diode arrays that integrate many elements.

The purpose of the present invention is to solve such problems,
An object of the present invention is to provide a semiconductor laser diode in which a double heterojunction and a buried layer can be grown simultaneously, and a method for manufacturing the same.

[Means to solve the problem]

The semiconductor laser diode of the present invention is a first semiconductor laser diode in which epitaxial growth of a semiconductor is difficult, in which a thin film such as a 5LOz, /VGaAs oxide film is provided on the surface of a semiconductor substrate.
and a second region in which epitaxial growth of a semiconductor is possible without providing the thin film, a polycrystalline semiconductor layer is formed on the first region, and a quantum well laser structure is formed using the epitaxial semiconductor on the second region. , and the quantum well laser structure is embedded in the polycrystalline semiconductor layer.

Further, the method for manufacturing a semiconductor laser diode of the present invention includes:
The above-mentioned first. a quantum well laser structure is formed by forming a second region and forming a polycrystalline semiconductor layer on the first region and simultaneously growing a semiconductor epitaxially on the second region; It is characterized in that it is manufactured by embedding it in the polycrystalline semiconductor layer.

To explain the present invention in detail, the present invention, as shown in FIG. This structure has the effect that a double heterojunction 1 and a polycrystalline 2 serving as a buried layer can be formed at the same time. Although the polycrystal 2 can be grown by several methods, details of this laser diode will be explained below using an example in which a SiO2 film is used. A 5LO2 film 4 (thin film) is deposited on the semiconductor substrate 3, and this film is removed only at the location where a double heterojunction is to be formed, and molecular beam epitaxy (MBE) is performed. Then, epitaxial growth is performed where the substrate surface is exposed, but polycrystalline 2 is grown on the deposited SiO2. This polycrystal 2 has a characteristic that it has a high resistivity and a refractive index lower than that of the quantum well active layer 5. Therefore,
The quantum valve door laser diode having the structure shown in FIG. 1 can satisfy two conditions necessary for a buried laser diode: current confinement and optical waveguide. As is clear from the above explanation, one MB is required to create this structure.
E-growth is sufficient and does not require regrowth.

Polycrystals have high resistance because carriers are captured in traps present at grain boundaries.

The reason why the refractive index is lower than that of the quantum well active layer is as follows. FIG. 2 shows an enlarged view of a portion 6 where the quantum well active layer 5 and the polycrystal 2 are in contact with each other, which is circled in FIG. Since the surface of multi-connected arrangement is not flat, the second
A quantum well 8 with irregularities as shown in the figure grows. At this time, since the molecular beam is obliquely incident on the portion shown by 9 which is inclined with respect to the substrate surface, a quantum well thinner than the single-layer gate 5 will grow after epitaxial growth. It is known that the refractive index of a quantum well decreases as the width of the quantum well decreases. Therefore, the refractive index of the portion indicated by 9 is smaller than that of the epitaxially grown quantum well 5. On the other hand, the quantum well 10 in the flat part
Since the well width is the same as that of the epitaxially grown quantum well 5, the refractive index is the same as that of the epitaxially grown quantum well 5.

Since the grain size of this polycrystal is small, ranging from several hundred to several thousand formulas, light takes the average value of the refractive index of the obliquely grown part and the flat part. Therefore, the refractive index of the polycrystalline portion is smaller than that of the epitaxial layer. For example, if a multilayer well with a width of 50 wells is grown and the surface area of the polycrystal is increased by 10%, the refractive index will decrease by 3×10 −2 . This is a value sufficient to guide light.

The difference between the present invention and the prior art, as is clear from what has already been stated, is that current confinement and optical waveguide are performed by the polycrystalline layer grown simultaneously with the double heterojunction.

〔Example〕

(Example 1) FIG. 3 is a schematic diagram of a striped laser diode embedded with polycrystal. This laser diode is
It was made using the following process.

First, a Si-doped GaAS substrate 1''2804:
The surface is etched with a H2O2:H2O (=5:1:1) mixture, and a 5i02 film 11 is deposited on this by vapor phase growth.
Deposit i ooo people. After removing the 5LO2 film 11 in stripes in the portion where the laser structure is to be formed by photolithography and hydrofluoric acid etching, the surface is cleaned with an aqueous hydrochloric acid solution. Next, a quantum well laser structure 12 is grown on this substrate by the MBE method. By this MBE growth, a laser structure 12 is grown in the portion where the SiO2 film 11 has been removed, and a polycrystalline 13 is grown on the SiO2. The laser structure includes, from the substrate side, an SL-doped GaAS buffer layer 14 (thickness 0.3 μm, carrier concentration 1X10"cm-3), Si-doped AJo, 4G
aO, GAS cladding layer 15 (thickness 1.0 μm, carrier concentration l×10”cm−3>, non-doped MO, 15Q
a0.85As optical waveguide layer 17 (thickness 0.1μTrL),
>>Doped GaAS/M Ga ASSO2
150,85 Shigeko well active layer 16〈Shiko well width 50 people, barrier layer width 5
0 people 1 Shuho 5), non-dope AJo, 1s Ga. 85
AS optical waveguide layer 17 (thickness 0.1 μTrL), Be-doped 7VO, 4Ga o6 AS cladding layer 18 (thickness 1.0
μm, carrier concentration l×1018 cm−3), Be-doped cap layer 19 (thickness 0.3 μm, carrier concentration 1×
It consists of 7 layers of 1019 cm-3). next,
Cr-AIj p contact 20 and A u G e
An NLn contact 21 is formed, and after R, the sample is cleaved to form a laser end face.

As is clear from the above steps, crystal growth was performed only once, and the yield of the laser diode was high.

This laser diode has a polycrystalline portion of 106Ω・cm.
Because of the high resistance, current confinement is achieved completely.

Furthermore, since the refractive index of the polycrystal in the portion corresponding to the ω Kozukido active layer is approximately 3×10 −2 smaller than that of the active layer, light is also confined. As a result, current confinement and light confinement occur simultaneously, making it possible to fabricate a low-threshold buried diode.

(Example 2) FIG. 4 shows the manufacturing process of a surface emitting diode embedded with polycrystal. This laser diode was made by the following process. First, Figure 4 (a
), an S-doped buffer layer 23 (thickness 0°3μ surface, carrier depth 1×1) is formed on S-doped GaAs 22.
018C "3), Si doped"0.3"aO, 7AS
Layer 24 (thickness 0.1μ carrier concentration 1×1018c)
3), non-doped GaAs protective layer 25 (thickness 0.01μ
m) is grown by metal organic vapor phase epitaxy or MBE. Using photolithography technology and selective etching of GaAS, the GaAs cap layer 25 is etched leaving only the circular dots 26 with a diameter of 5 μm (
(See Figure 4(b)). At this time, the exposed /VGaAS
portion serves to grow polycrystals. This is because the surface of AlGaAs is oxidized by contact with air, and this #G
This is because the stability of the aASW compound prevents epitaxial growth on it (in this example,
This /VGaAsM compound layer becomes an a film that hinders epitaxial growth). Next, this sample is placed in an MBE apparatus and heated at 750° C. while being irradiated with an As beam to evaporate the circular GaAS dots 26 left on the surface. On top of this, as shown in FIG. 4(C), SL dope "0.3"
Ga□, 7AS cladding layer 27 (thickness 2.5 μm, carrier concentration 1X10'8u+-3'), Be doped G
aAs/# GaO, 150, 85 AS multiple quantum well active layer 28 (quantum well width 50 people.

Barrier layer width 50 people 1 cycle 300. Carrier concentration 1×10I
7c "3), Be doped M o, 3G a o, 7A
S cladding layer 29 (thickness 2.5 μm, carrier concentration 1×
1018cm-3), Be-doped M0.1”, a □1
A gAS cap layer 30 (thickness 0.2 μm, carrier concentration IX10I1X1019) is grown by MBE. Through this growth, a laser structure grows only in the part where the GaAs dot 26 was, and the other part becomes a polycrystalline 31.Next A 5L3N4 film with a diameter of 3 μm was deposited on the growth surface, and a 5L3N4 film with a diameter of 3 μm was deposited on the lede part by photolithography technology.
Etching is performed so that a circle remains, and Au/Zn is deposited on it. The remaining circular portion of the 5L3N3 film functions as a reflecting mirror 32, and the remaining portion functions as an n-contact 33 (see FIG. 4(d)). Also, HCj:CH
3CO0H:H202 (=1:2:1) f1 mixture The GaAs substrate under the teleser structure was removed, and the Au/5
Form L3N4 reflection #134 and n-contact 35.

(See Figure 4(e)). As shown in FIG. 5, this surface emitting laser diode is mounted on a heat sink 37 with the substrate side facing up, and laser light 36 is extracted from the substrate side.

Although this process includes two MBE growths, it does not require complicated steps such as embedding a laser structure, so the yield is high. Further, since current confinement is completely performed, the threshold value is also low.

In Example 1.2, Si
02 or AlGaAs was used, but in addition to this, SL
3N4, fiJ203, and Si can also be used.

〔Effect of the invention〕

As described above, in the laser diode of the present invention, the buried layer and the laser structure can be grown simultaneously.

Therefore, it has the characteristics of a low threshold value and a high yield. This is an important advantage for use in 0EICs and surface emitting laser arrays.

Further, according to the method for manufacturing a laser diode according to the present invention, the number of manufacturing steps is reduced compared to conventional methods, so that the cost of the product can be reduced.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of the configuration of an m-valve door laser diode according to the present invention, Fig. 2 is an enlarged view of the main part of Fig. 1, and Fig. 3 is an m-valve door stripe shown as an embodiment of the present invention. A schematic configuration diagram of a laser diode, FIGS. 4(a) to (e) are manufacturing process diagrams of a polycrystalline buried surface emitting laser diode shown as another embodiment of the present invention, and FIG. 5 is a diagram of FIG. 4(a). ~(e
) is a completed diagram of the polycrystalline buried surface emitting laser diode shown in FIG. DESCRIPTION OF SYMBOLS 1... 1 child valve door laser structure, 2... Polycrystalline semiconductor layer, 3... Semiconductor substrate, 4... Thin film. X2+ Figure 4

Claims (2)

[Claims] (1) In a buried semiconductor laser diode, there is a first region where epitaxial growth of a semiconductor is difficult, where a thin film such as SiO_2 or AlGaAs oxide film is provided on the surface of the semiconductor substrate, and epitaxial growth of a semiconductor without the above thin film is possible. a second region is formed, and the first region is
A polycrystalline semiconductor layer is formed on the region, and a quantum well laser structure made of an epitaxial semiconductor is formed on the second region,
A semiconductor laser diode characterized in that the quantum well laser structure is embedded in the polycrystalline semiconductor layer. (2) In the method for manufacturing an embedded semiconductor laser diode, SiO_2, AlGaAs, etc. are placed on the surface of the semiconductor substrate.
forming a first region in which it is difficult to epitaxially grow a semiconductor provided with a thin film such as an oxide film, and a second region in which epitaxial growth of a semiconductor is possible without providing the thin film;
A quantum well laser structure is formed by forming a polycrystalline semiconductor layer on the first region and simultaneously epitaxially growing a semiconductor on the second region, and embedding the quantum well laser structure in the polycrystalline semiconductor layer. 1. A method for manufacturing a semiconductor laser diode, the method comprising: manufacturing a semiconductor laser diode.