JPH077863B2 - Visible semiconductor laser device - Google Patents

Description

The present invention relates to an AlGaInP-based visible light semiconductor laser device.

(B) Conventional technology AlGaInP has a band gap of 0.6 μm band and is used as a material for visible light semiconductor laser devices.

FIG. 6 shows a conventional AlGaInP-based semiconductor laser device, for example, Proceedings of the Autumn Society of Applied Physics 1988, 4p-ZC-10, 836.
It is disclosed on the page.

In the figure, (11) is a substrate made of n-type GaAs, and (12) is n.
Type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P n-type cladding layer, (1
3) is an active layer made of undoped (Al _X Ga _1-X ) _0.5 In _0.5 P, and (14) is a p-type clad layer made of p-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P. These layers are sequentially epitaxially grown on one main surface of the substrate (11) by using the well-known MOCVD method, MBE method or the like. A ridge having a width of 5 μm is formed on the p-type cladding layer (14) by etching.

(15) is a block layer made of n-type GaAs epitaxially grown on the p-type clad layer (14), and is a p-type mask layer.
It is not laminated on the ridge top of the mold cladding layer (14). (16) is p-type Ga epitaxially grown on the exposed top of the p-type cladding layer (14) and the block layer (15).
It is a cap layer made of As.

(17) is a p-type electrode made of Au / Zn / Au formed on the cap layer (16), and (18) is an n-type electrode made of AuGe / Au formed on the other main surface of the substrate (11). Is.

In such a device, when the Al composition ratio of the active layer (13) is x = 0.1, laser light having a wavelength of 649 nm can be obtained.

On the other hand, currently, measuring instruments and POS (poi
A He-Ne laser with a wavelength of 632.8 nm is used as the light source of the barcode scanner used in the nt of sales system. Therefore, an AlGaInP-based semiconductor laser device that can oscillate at the same wavelength as the He-Ne laser, is lightweight, small-sized, and has low power consumption is desired as a light source to replace the He-Ne laser. For this reason, it is necessary to oscillate the above conventional device at a shorter wavelength.

As a method of shortening the wavelength of AlGaInP-based semiconductor laser devices, increase the Al composition ratio of the active layer. Make the active layer a superlattice structure (Electronics Letters, V
ol.24, No.24 (1988), p.1489) The growth temperature of each layer is higher than 700 ℃ (Japanese Jour.
nal of Applied Physics, Vol.27, No.11 (1988), p.2
098) Diffusing Zn into active layer (IEEE, Journal of Quantum
Electronics, QE-23, No.6 (1987), p.704).

However, in the above method, the crystallinity of the active layer (13) decreases as the Al composition ratio increases, so that the oscillation threshold value increases and continuous operation becomes difficult. For example, active layer (13)
If the Al composition ratio of x is 0.2, the oscillation wavelength is 630 to 640 nm.
However, the oscillation threshold current density is 10 kA / cm ² or more, which is not practical.

Further, in the methods (1) and (2), the oscillating operation of the device becomes unstable and the active layer (13) deteriorates significantly, so that there arises a problem that the manufacturing yield of the device is low and the life is short.

(C) Problem to be Solved by the Invention Therefore, the present invention provides an AlGaInP-based visible light semiconductor laser device having a low oscillation threshold of the device, a high manufacturing yield, and a long life.

(D) Means for Solving the Problem The present invention is directed to a GaAs substrate having a main surface inclined by 5 degrees or more in the [011] direction from the (100) surface, and an Al formed on the main surface.
And an AlGaInP-based semiconductor layer including an active layer made of GaInP, wherein the Al composition ratio of the AlGaInP in the active layer is greater than 0 and 0.15 or less.

(E) Action The present invention is directed to a GaAs substrate whose main surface is a surface inclined by 5 degrees or more from the (100) surface in the [011] direction, and an Al formed on the main surface.
An AlGaInP-based semiconductor layer including an active layer made of GaInP, and the Al composition ratio of the AlGaInP of the active layer is set to be larger than 0 and 0.15 or less.
The wavelength of the oscillated light can be shortened while making it larger and 0.15 or less as much as possible. Therefore, when the desired wavelength is obtained, the increase in threshold current can be suppressed more than in the conventional case. Moreover, according to the constitution of the present invention, the above-mentioned active layer has improved crystallinity and good crystallinity, so that the manufacturing yield and the life of the device of the present invention are increased.

(F) Example In the present invention, the band gap of the AlGaInP-based semiconductor layer is GaA.
s Phenomenon that changes depending on the plane orientation of the substrate, that is, 5 from the (100) plane to the [011] direction on the growth surface of the GaAs substrate.
By utilizing a surface inclined by more than one degree, the phenomenon in which the band gap of the AlGaInP-based semiconductor layer formed thereon is widened is utilized. Moreover, this phenomenon was first discovered by the present inventors.

FIG. 2 shows an example of such a phenomenon. In this figure, one main surface of the GaAs substrate is tilted in various directions from the (100) plane in the [011] direction, and the peak energy is measured from the photoluminescence (PL) of Ga _0.5 In _0.5 P formed on this. Also this Ga
_0.5 In _0.5 P is a reduced pressure MOCV with a growth temperature of 710 ° C and a growth pressure of 70 Torr.
It was formed using the D method. As is clear from the figure, the peak energy increases as the tilt angle increases, and becomes saturated when the tilt angle becomes 5 ° or more.

FIG. 3 shows that when Ga _0.5 In _0.5 P is formed on one main surface of the substrate and (Al _X Ga _1-X ) _0.5 In _0.5 P (X ≧ 0) is formed thereon (Al
_It shows the peak wavelength of photoluminescence with respect to the Al composition ratio of ( _X Ga _1-X ) _0.5 In _0.5 P. Here, as one main surface of the substrate, 0 °, 5 ° from the (100) plane in the [011] direction,
The surfaces inclined by 7 ° were used respectively. As an example, FIGS. 4 and 5 show the photoluminescence spectra when the Al composition ratio x is 0.15 and the tilt angle of the substrate is 0 ° and 5 °. Moreover, all measurements were performed at room temperature.

As is apparent from FIG. 3, the amount of change in the peak wavelength due to the substrate inclination is substantially constant regardless of the Al composition ratio x.
For example, as shown in FIGS. 4 and 5, Al composition ratio x =
When it is 0.15, the peak wavelengths of tilt angles 0 ° and 5 ° are 642.2n respectively.
m, 622.0 nm, and the amount of change is about 20 nm. Also,
The peak wavelength with respect to the tilt angle of the substrate is 5 ° as in the case of Ga _0.5 In _0.5 P shown in Fig. 2 regardless of the Al composition ratio x.
The above tended to be saturated.

From the above, it is apparent that in the AlGaInP-based semiconductor laser device, the wavelength can be shortened by using a plane inclined from the (100) plane in the [011] direction as one main surface of the substrate. However, a plane inclined by 5 ° or more, preferably 5-7 ° in the [011] direction from the (100) plane is selected as one main surface of the substrate in the present invention. This is because in addition to the maximum and similar wavelength change can be obtained when the tilt angle is 5 ° or more, Ga _0.5 In _0.5 P and (Al _X Ga _1-X ) _0.5 In _0.5 P formed on this surface This is because the crystal defects are sharply reduced and the crystallinity is improved. For example, Ga _0.5 In _0.5 P formed on the (100) plane of the substrate had about 10,000 crystal defects called hillocks / cm ² , but 100 planes / cm ² or less on the 5 ° inclined plane. Becomes That is, according to the present invention, the Al composition ratio of the active layer is reduced as much as possible in order to achieve a desired short wavelength by using an inclined surface of 5 ° or more from the (100) plane to the [011] direction as the main surface of the substrate. It is possible to improve the crystallinity of the active layer as well as to suppress the reduction of the crystallinity of the active layer by reducing the size.

FIG. 1 shows an embodiment of the device of the present invention.

In the figure, (1) is an n-type with a carrier concentration of 2 × 10 ¹⁸ cm ^-3
The substrate is made of GaAs, and one main surface (1a) thereof is inclined by 5 ° or more, for example, 5 ° in the [011] direction from the (100) surface by polishing.

(2) is a buffer layer, (3) is an n-type cladding layer, (4)
Is an active layer, (5) is a p-type cladding layer, and (6) is a cap layer. These layers have a growth temperature of 620 to 670 ° C., for example 670 ° C.
Using a low pressure MOCVD method with a reaction chamber pressure of 70 Torr, they are sequentially laminated on one main surface (1a) of the substrate (1). The table below shows other conditions for forming these layers.

(7) is a block layer made of SiO ₂ laminated on the cap layer (6) by a sputtering method, and a stripe groove (8) having a width of 6 μm reaching the cap layer (6) is formed by etching.

(9) is Au / Cr in which a Cr film and an Au film are vacuum-deposited in this order on the exposed cap layer (6) and block layer (7).
A p-type electrode made of an electrode, (10) a Cr film, a Sn film, and an Au film were vacuum-deposited in this order on the other main surface (1b) of the substrate (1).
It is an n-type electrode composed of Au / Sn / Cr electrodes. These electrodes
The heat treatment at 400 ° C. makes ohmic contact with the cap layer (6) or the substrate (1).

A known intermediate layer made of Ga _0.5 In _0.5 P may be provided between the cap layers (6) of the p-type cladding layer (5) for the purpose of suppressing an increase in operating voltage of the device.

As described above, in the present embodiment, the so-called oxide stripe structure in which SiO ₂ is used for the block layer (7) has been described, but the present invention is not limited to the inner stripe structure such as the conventional device shown in FIG. Can also be easily applied.

Further, in the device of this embodiment, the Al composition ratio x of the active layer (4) is set to 0.
15, but the present invention is not limited to this,
Of course, various values are selected to obtain the desired wavelength. For example, to replace the He-Ne laser,
When obtaining a wavelength of about 30 nm, for example, the inclination angle of the substrate (1) is 5 ° and the Al composition ratio x of the active layer (4) is 0.1 to 0.15.
It should be done.

(G) Effect of the Invention The present invention provides a GaAs substrate whose main surface is a surface inclined by 5 degrees or more from the (100) surface in the [011] direction, and an Al formed on the main surface.
An AlGaInP-based semiconductor layer including an active layer made of GaInP, and the Al composition ratio of the AlGaInP of the active layer is set to be larger than 0 and 0.15 or less.
The wavelength of the oscillated light can be shortened while making it as large as possible and as small as 0.15 or less. Therefore, when the desired wavelength is obtained, the increase in threshold current can be suppressed more than in the conventional case. Moreover, according to the constitution of the present invention, the above-mentioned active layer has improved crystallinity and good crystallinity, so that the manufacturing yield and the life of the device of the present invention are increased.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the device of the present invention, FIG. 2 is a characteristic diagram showing PL peak energy with respect to a substrate tilt angle, FIG. 3 is a characteristic diagram showing peak wavelength with respect to Al composition ratio, and FIG.
5 and 5 are PL spectrum characteristic diagrams when the Al composition ratio is 0.15 and the tilt angles of the substrate are 0 ° and 5 °, respectively, and FIG. 6 is a sectional view showing a conventional device.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takao Yamaguchi 2-18 Keihan Hondori, Moriguchi City, Osaka Sanyo Electric Co., Ltd. (56) Reference JP-A-1-128423 (JP, A)

Claims (1)

[Claims] 1. A GaAs substrate whose main surface is a surface inclined by 5 degrees or more from the (100) surface in the [011] direction, and formed on the main surface.
A visible light semiconductor laser device, comprising: an AlGaInP-based semiconductor layer including an active layer made of AlGaInP;