JPH03227586A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To obtain a high quality semiconductor laser whose dislocation is decreased by specifying the longitudinal direction of a laser resonator and the shape of the junction part between a III-V compound semiconductor layer and a silicon single crystal substrate. CONSTITUTION:The junction part between a silicon single crystal substrate 10 and a III-V compound semiconductor layer forms a stripe shape having the width of 10mum or less has a stripe whose width is 10mum or less. The longitudinal direction of the stripe (in parallel with the length of a resonator) is inclined by 10 deg. or more within a plane {100} with respect to the direction of [011] of the silicon single crystal substrate 10. Thus, the length in the direction in parallel with the direction of [011] of the junction part becomes 100mum or less. Therefore, the high-quality compound semiconductor layer having less dislocation can be formed. As a result, the high-quality semiconductor laser having the low threhold value can be formed.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a semiconductor laser.

[Conventional technology]

When forming a semiconductor laser consisting of a ■-V group compound semiconductor layer on a silicon single crystal substrate, problems with crystal growth technology include the difficulty of surface cleaning and the large difference in lattice constant. In particular, while soricons are covalent crystals, the ■-v group compound semiconductors are polarizable crystals. Because of these problems, compound semiconductor layers grown on silicon substrates have high dislocations of about 10'cm-'', making it difficult to obtain sufficient quality for device fabrication.

Methods to reduce these problems include cleaning the substrate surface at high temperatures, using a buffer layer consisting of a strained superlattice layer, and tilting the substrate orientation. An example of a semiconductor laser made by forming a ■-■ group compound semiconductor made of InP is reported in 7 Pride Physics Letters, Vol. 53, No. 9, p. 725, 1988. In this conventional example, a threshold current density of 10 K A/cJ is obtained for the semiconductor laser.

[Problem to be solved by the invention]

However, in the above conventional example, a normal semiconductor laser using a lattice-matched compound semiconductor substrate has a power of 1 to 2 KA/cn.
The threshold current density is several times higher than that of i, indicating that the crystal quality is insufficient. This is because in the case of a semiconductor laser, which is a device that is relatively sensitive to dislocations, it is necessary to suppress the dislocation density to less than 10 cm, but in the conventional example described above, the dislocation density is not sufficiently reduced and the light emission characteristics of the crystal are not good. .

An object of the present invention is to provide a high quality semiconductor laser using a silicon single crystal as a substrate.

[Means to solve the problem]

The present invention provides a semiconductor laser formed by laminating multiple layers of ■-■ group compound semiconductors in a stripe shape on a silicon single crystal substrate having a plane orientation near the (,100) plane, in which the laser resonator length direction is It forms an angle of 10° or more from a direction parallel to the [011] direction of the single-crystal substrate, and the shape of the bonding portion between the compound semiconductor layer and the silicon single-crystal substrate has a width of 10°.
This structure is characterized by a stripe shape of μm or less.

[Effect]

In the semiconductor laser according to the present invention, the joint portion between the silicon single crystal substrate and the compound semiconductor layer has a stripe shape with a width of 10 μm or less, and the longitudinal direction of the stripe (parallel to the resonator length) is [ 0,11]
It is formed at an angle of 10° or more in the (100) plane with respect to the direction. As a result, the length of the striped joint in the direction parallel to the [011] direction is at most 5
7 μm, which is significantly smaller than when the resonator length direction is parallel to the [011] direction. Generally, when a compound semiconductor layer is stacked on a silicon single crystal substrate, the [01
1] Dislocations occur along directions parallel to the direction, and dislocations perpendicular to each other further generate new dislocations. Such an increase in dislocations can be suppressed by reducing the length of the joint in the direction parallel to the [011] direction, and in particular, 1
Dislocations are significantly reduced below 00 μm. In the present invention, the length of the joint portion in the direction parallel to the [011] direction is 1
00 μm or less, a high-quality compound semiconductor layer with few dislocations can be formed, and as a result, a high-quality semiconductor laser with a low threshold value can be formed.

〔Example〕

Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 is a perspective view of a semiconductor laser showing an embodiment of the present invention. In this example, the (1
In doped with silicon to lXlO”ctn-3 on a silicon single crystal substrate IO whose surface is
P buffer layer 12, undoped InGaAsP active layer 13 with forbidden band width 0.95 eV, beryllium 1×10
A double heterostructure was formed consisting of an InP cladding layer 14 doped with "cm-" and an InGaAsP contact layer 15 doped with beryllium lXIO"Cm-3. The Si02 layer 11 was made of InP and InGaA.
This is a selective growth mask for selectively epitaxially growing sP to create a striped double heterostructure. The current flows along the p-type electrode 17, the contact layer 15, the cladding layer 14, the active layer 13, the buffer layer 12, the silicon single crystal substrate IO and the n-type electrode 18, and the organic insulator layer 1
6 and 1 on the high layer 11.

In this example, a chemical beam epitaxial growth method was used as an epitaxial growth method having selective growth characteristics. Triethyl gallium (abbreviated as TEG) is an m-group material.
Molecular formula (C2Hs) 3 Ga) and trimethylindium (abbreviation TMI, molecular formula (CH3) 3 I n
), arsine (molecular formula ASH3) and phosphine (molecular formula PH3) were used as group V materials, and epitaxial growth was performed by irradiating these gases onto a silicon single crystal substrate 10 heated and maintained at the growth temperature in a high vacuum. . Note that, before growth, surface cleaning was performed at high temperature (1000° C.) as a general method for surface cleaning and single domain formation.

In this example, first, S
An i02 layer 11 was formed, and the surface of the silicon single crystal was exposed in stripes having a width of 3.5 μm using conventional photolithography and chemical etching methods. Next, a double heterostructure was formed by selectively growing a precursor compound semiconductor by chemical beam epitaxial growth using the 5i02 layer 11 as a selective growth mask. Next, a polyimide layer is formed as an organic insulating layer 16 on both sides of the striped double heterostructure, and a p-type electrode 17 and an n-type electrode 18 are formed on the top of the double heterostructure and the back surface of the substrate, respectively, to form a semiconductor laser. And so.

FIG. 2 shows the bonding portion 20 between the SoliFun single crystal substrate 10 and the buffer layer 12, which is a compound semiconductor layer, in the [011] direction (the notation for the compound semiconductor layer is [011]) in this embodiment.
and [011]); FIG. In the figure, the upward direction perpendicular to the plane of the paper is taken as <100>.

The joint portion 20 has a stripe shape with a width of 3.5 μm,
Set the resonator direction to (45° (100) with respect to the 01D direction)
Tilt within the plane. At this time, [01
1] The length L in the direction parallel to the direction is sufficiently small as 5 μm, and as a result, the increase in dislocations is significantly suppressed and the dislocation density can be suppressed to 10′ cm −′ or less.

Although the chemical beam growth method was used in the above embodiment, it can also be realized by using other epitaaxial growth methods having selective growth characteristics, such as liquid phase epitaxy, organometallic vapor phase epitaxy, or chloride vapor phase epitaxy.

In the above embodiment, InGaAsP/InP semiconductor material was used, but Ga A j2 A s / Ga,
As.

It is also applicable to semiconductor lasers made of other m-v group bioconductive materials such as I n Ga A (!A s / I n P).

〔Effect of the invention〕

The semiconductor laser according to the present invention has a high-quality compound semiconductor layer with a reduced dislocation density by tilting the direction of the cavity length, so that it can achieve light emission characteristics comparable to those of a semiconductor laser using a compound semiconductor substrate.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a semiconductor laser which is an embodiment of the present invention, and FIG. 2 is an explanatory diagram of the resonator length direction of the present invention. lO...Silicon single crystal substrate, 11...
・SiO2 layer, 12...Buffer layer, 13.
... Active layer, 14 ... Cladding layer, 15
...Contact layer, 16--Organic insulator layer, 17--P type electrode, 18--N type electrode, 20--Junction Each part is shown below.

Claims (1)

[Claims] In a semiconductor laser formed by laminating multiple layers of III-V compound semiconductors on a silicon single crystal substrate having a plane orientation near the {100} plane, the laser cavity length direction is the [011] direction of the silicon single crystal substrate. A semiconductor characterized in that the bonding portion between the III-V compound semiconductor layer and the silicon single crystal substrate has a stripe shape with a width of 10 μm or less, forming an angle of 10° or more from a direction parallel to the semiconductor layer. laser.