JP2804737B2 - Visible light semiconductor light emitting device and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a visible light semiconductor light emitting device and a method for manufacturing the same.

[0002]

2. Description of the Related Art AlGaInP has a band gap of 0.6 μm band and is a visible light semiconductor laser device (light emitting device).
Used as a material.

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

[0004] In the figure, (11) shows the case of n-type GaAs.
(12) is an n-type (Al_{0. 7}Ga_0.3)_0.5In
_0.5N-type cladding layer made of P;
(Al_xGa_1-x)_0.5In_0.5P active layer, (1
4) is p-type (Al_0.7Ga_0.3) _0.5In_0.5P consisting of P
Mold cladding layer. These layers are well known MOCVD
On one main surface of the substrate (11) by using the MBE method, the MBE method, or the like.
It is epitaxially grown. The p-type cladding layer (1
In 4), a ridge having a width of 5 μm was formed by etching.
Have been. (15) is formed on the p-type cladding layer (14).
Block layer made of n-type GaAs grown by axial growth
Then, the top of the ridge of the p-type cladding layer (14) is formed by using a mask.
Is not laminated. (16) is an exposed p-type crack.
Epitaxy on top of the doped layer (14) and on the block layer (15).
With a cap layer made of p-type GaAs grown
is there.

[0005] (17) is a p-type electrode made of Au / Zn / Au formed on the cap layer (16), and (18) is made of AuGe / Au formed on the other main surface of the substrate (11). It is an n-type electrode.

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

On the other hand, at present, a light source having a wavelength of 63 is used as a light source of a bar code scanner used for a measuring instrument using visible laser light or a POS (point of sales) system.
A 2.8 nm He-Ne laser is used. Therefore, an AlGaInP-based semiconductor laser device which can oscillate at the same wavelength as that of the He-Ne laser, is lightweight, small-sized, and consumes low power is desired as a light source replacing the He-Ne laser. For this reason, it is necessary to oscillate the conventional device at a shorter wavelength.

As a method for shortening the wavelength of an AlGaInP-based semiconductor laser device (light emitting device), an Al composition ratio of the active layer is increased. The active layer has a superlattice structure (Electronics Letters, Vo).
l.24, No.24 (1988), p1489) The growth temperature of each layer should be higher than 700 ℃ (Japanese J
ournal of Applied Physics, Vol. 27, No. 11 (1988), p. 209
8) Zn is diffused into the active layer (IEEE, Journal of Q
uantum Electronics, QE-23, No. 6 (1987), p. 704).

However, in this 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, when the Al composition ratio of the active layer (13) is x = 0.2, the oscillation wavelength becomes 630 to 640 nm, and He-Ne
Although it becomes substantially equal to the wavelength of the laser, the oscillation threshold current density becomes 10 kA / cm ² or more, which is not practical.

Further, in the method (1), the oscillation operation of the device becomes unstable, and the active layer (13) is greatly deteriorated. Therefore, there are problems that the production yield of the device is low and the life is short.

[0011]

Accordingly, the present invention provides an AlGaInP having a high production yield and a long life.
It is an object of the present invention to provide a system-based visible light semiconductor light emitting device and a method for manufacturing the same.

[0012]

The first visible light semiconductor light emitting device according to the present invention is a semiconductor device having a visible light in the [011] direction from the (100) plane.
A GaAs substrate having a major surface inclined at an angle of not less than °, a buffer layer of GaInP formed on the major surface, and an AlGaInP-based semiconductor layer including an active layer of AlGaInP formed on the buffer layer. It is characterized by having.

Further, a second visible light semiconductor light emitting device of the present invention has a GaAs substrate having a main surface inclined at least 5 ° in the [011] direction from the (100) plane, and a GaAs substrate formed on the main surface. A buffer layer made of GaInP, a first clad layer made of AlGaInP formed on the buffer layer, and an AlGaInP formed on the first clad layer.
And an AlGaI layer formed on the active layer.
and a second cladding layer made of nP.

Further, in the third visible light semiconductor light emitting device of the present invention, a surface inclined by 5 ° or more in the [011] direction from the (100) plane is defined as one main surface, and the other main surface opposite to the one main surface is used. A first conductivity type GaAs substrate on which a first conductivity type electrode in ohmic contact is formed on a surface, a first conductivity type buffer layer made of GaInP formed on the one main surface, and the buffer layer A first conductivity type clad layer made of AlGaInP formed thereon, an active layer made of AlGaInP formed on the first conductivity type clad layer, and a second made of AlGaInP formed on the active layer; It is characterized by comprising a conductive type clad layer and a second conductive type electrode which is in ohmic contact with the second conductive type clad layer via a cap layer. In particular, the angle of the inclined surface of 5 degrees or more may be set so that the amount of change in the peak wavelength is about 20 nm or less as compared with the case where the angle is 0 degree.

In the first method of manufacturing a visible light semiconductor light emitting device according to the present invention, the [0]
[11] A buffer layer made of GaInP and an AlGaInP-based semiconductor layer including an active layer made of AlGaInP are decompressed in this order on a plane inclined by 5 ° or more in the [11] direction.
It is characterized by being formed by the VD method.

Further, in the second method for manufacturing a visible light semiconductor light emitting device according to the present invention, the [0]
11], a buffer layer made of GaInP, a first clad layer made of AlGaInP, an active layer made of AlGaInP, AlGaInP
The second cladding layer composed of
It is formed by a method.

[0017]

[0018]

[0019]

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is directed to a phenomenon in which the band gap of an AlGaInP-based semiconductor layer changes depending on the plane orientation of a GaAs substrate, that is, from the (100) plane to the [011] plane. By using a surface inclined 5 degrees or more in the direction, the AlG
This utilizes the phenomenon that the band gap of the aInP-based semiconductor layer is widened. This phenomenon was first discovered by the present inventors.

FIG. 2 shows an example of such a phenomenon. FIG.
One main surface of the As substrate is moved from the (100) plane to the [011] direction.
Various inclinations, Ga formed on this_0.5In_0.5P's photo
Peak energy was measured from luminescence (PL)
Things. In addition, this Ga _0.5In_0.5P is growth temperature 7
Using a reduced pressure MOCVD method at 10 ° C and a growth pressure of 70 Torr
It was formed. As can be seen from the figure, the slope
As the angle increases, the peak energy increases, and the inclination angle increases.
Becomes more than 5 °, the saturation occurs.

FIG. 3 shows that Ga _0.5 In _0.5 P is formed on one main surface of the substrate.
Is formed thereon, and (Al _x Ga _{1 -x} ) _0.5 In _0.5 P (x
The peak wavelength of photoluminescence with respect to the Al composition ratio of (Al _x Ga _1-x ) _0.5 In _0.5 P when ≧ 0 is formed. Here, as one main surface of the substrate, (1
The planes inclined at 0 °, 5 °, and 7 ° in the [011] direction from the (00) plane were used. As an example, FIGS. 4 and 5 show photoluminescence spectra when the Al composition ratio x is 0.15 and the tilt angles of the substrate are 0 ° and 5 °. All measurements were performed at room temperature.

As is apparent from FIG. 3, the amount of change in the peak wavelength due to the inclination of the substrate is substantially constant irrespective of the Al composition ratio x. For example, as shown in FIGS.
When the composition ratio x = 0.15, the peak wavelengths at the inclination angles of 0 ° and 5 ° are 642.2 nm and 622.0 nm, respectively, and the amount of change is about 20 nm. Further, the peak wavelength with respect to the tilt angle of the substrate tends to saturate at 5 ° or more as in the case of Ga _0,5 In _0,5 P shown in FIG. 2 regardless of the Al composition ratio x. Was.

As described above, in the AlGaInP-based semiconductor laser device (light emitting device), (10
It is clear that the wavelength can be shortened by using a plane inclined in the [011] direction from the 0) plane. However, one principal surface of the substrate in the present invention is [01] from the (100) plane.
1] A plane inclined by 5 ° or more, preferably 5 to 7 ° in the direction is selected. This is because the maximum and the same wavelength change can be obtained when the inclination angle is 5 ° or more, and Ga _0.5 In _0.5 P and (Al _x Ga _{1 -x} ) _0.5 In _0.5 formed on this surface.
This is because crystal defects are rapidly reduced from P and crystallinity is improved. For example, Ga formed on the (100) plane of the substrate
_0.5 In _0.5 P has about 10 crystal defects called hillocks.
000 / cm ^{2 were} generated, but on a surface inclined at 5 °, the number was 100 / cm ² or less. That is, according to the present invention, by using an inclined surface of 5 ° or more from the (100) plane to the [011] direction on one principal surface of the substrate, the Al composition ratio of the active layer can be reduced as much as possible to achieve a desired short wavelength. In addition to reducing the size, the crystallinity of the active layer can be improved as well as suppressing the decrease in the crystallinity of the active layer.

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

In the figure, (1) shows a carrier concentration of 2 × 1
A substrate made of n-type GaAs of 0 ¹⁸ cm ⁻³ , one main surface (1a) of which is inclined by 5 ° or more, for example, 5 ° from the (100) plane in the [011] direction by polishing.

(2) is a buffer layer, (3) is an n-type (Al
_x1 Ga _1-x1) cladding layer formed of _{y1 In 1-y1 P, (} 4)
Is an active layer, and (5) is a p-type (Al _x2 Ga _1-x2 ) _y2 In _1-y2
P is a cladding layer, and (6) is a cap layer. These layers are formed on one main surface (1a) of the substrate (1) using a reduced pressure MOCVD method at a growth temperature of 620 to 670 ° C., for example, 670 ° C., and a reaction chamber pressure of 70 Torr. ). The following table shows other conditions for forming these layers.

[0028]

[Table 1]

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

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

In such a semiconductor laser device, since the wavelength can be shortened, an increase in threshold current can be suppressed as compared with the related art when a desired wavelength is obtained. In addition, the active layer has improved crystallinity and good crystallinity, so that the production yield is increased and the life is prolonged.

In order to suppress an increase in the operating voltage of the device, a G layer between the p-type cladding layer (5) and the cap layer (6) is used.
a _0.5 an In _0.5 the known intermediate layer may be provided consisting of P.

While the present embodiment has been described with reference to a so-called oxide stripe structure using SiO ₂ for the block layer (7), the present invention is not limited to an inner stripe structure such as the conventional device shown in FIG. It can be easily applied to the structure of FIG.

In the device of this embodiment, the Al composition ratio x of the active layer (4) is set at 0.15. However, the present invention is not limited to this. Is of course selected. For example, when a wavelength of about 630 nm is obtained for the purpose of substituting a He-Ne laser, for example, the inclination angle of the substrate (1) is set to 5 °, and the Al composition ratio x of the active layer (4) is set to 0.1 to 0. It may be set to 15.

According to the present invention, an AlGaInP-based semiconductor layer formed on a crystal growth surface of the GaAs substrate is formed on the crystal growth surface by using a surface inclined by 5 ° or more in the [011] direction from the (100) plane. And the Al composition ratio x is small (Al _x Ga _{1 -x} ) _y I
The crystallinity of the active layer is improved, as well as the decrease in the crystallinity of the active layer composed of n _1-y P (x <x1, x2) is suppressed.

In particular, the buffer layer (particularly, GaInP buffer layer) formed on the crystal growth surface has very few crystal defects, so that the crystallinity of the active layer is particularly improved.

[0037]

According to the present invention, the use of a surface inclined at an angle of 5 ° or more from the (100) plane in the [011] direction from the (100) plane to the main surface of the GaAs substrate reduces the wavelength of the AlGaInP-based semiconductor light emitting device and reduces the active layer. Crystallinity can be improved. Therefore,
In addition to using the inclined surface, by selecting a small Al composition ratio of the active layer, it is possible to improve the crystallinity of the active layer made of AlGaInP while realizing a desired short wavelength, and to manufacture a device. High yield and long service life.

[Brief description of the 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 a peak wavelength with respect to an Al composition ratio.

FIG. 4 shows an Al composition ratio of 0.15 and a tilt angle of the substrate of 0.
FIG. 9 is a PL spectrum characteristic diagram when the angle is set to °.

FIG. 5 shows that the Al composition ratio is 0.15, and the inclination angle of the substrate is 5
FIG. 9 is a PL spectrum characteristic diagram when the angle is set to °.

FIG. 6 is a sectional view showing a conventional device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 GaAs substrate 1 a one main surface 2 GaInP buffer layer 3 AlGaInP-based cladding layer 4 AlGaInP active layer 5 AlGaInP-based cladding layer

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Takao Yamaguchi 2-18-18 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (56) References JP-A-1-128423 (JP, A) JP-A 2-260682 (JP, A) JP-A-1-183498 (JP, A) JP-A-1-262686 (JP, A) JP-A-2-213185 (JP, A) JP-A-1-154513 (JP, A) A) (58) Field surveyed (Int. Cl. ⁶ , DB name) H01S 3/18 H01L 33/00

Claims (5)

(57) [Claims] 1. An angle of 5 ° from a (100) plane in a [011] direction.
A GaAs substrate having the inclined surface as a main surface, a buffer layer of GaInP formed on the main surface, and an AlGaInP-based semiconductor layer including an active layer of AlGaInP formed on the buffer layer. A visible light semiconductor light emitting device, comprising: 2. 5 ° from (100) plane in [011] direction
A GaAs substrate having the above-described inclined surface as a main surface, a buffer layer made of GaInP formed on the main surface, a first cladding layer made of AlGaInP formed on the buffer layer, AlG formed on cladding layer
an active layer made of aInP, and A formed on the active layer
a visible light semiconductor light emitting device, comprising: a second cladding layer made of lGaInP . 3. 5 ° from (100) plane in [011] direction
The inclined surface is defined as one main surface, and the other main surface on the opposite side to the one main surface.
An electrode of a first conductivity type in ohmic contact is formed on the surface;
A GaAs substrate of the first conductivity type,
First conductivity type buffer layer of GaInP formed
And AlGaInP formed on the buffer layer.
A first conductivity type cladding layer, and the first conductivity type cladding layer
An active layer of AlGaInP formed on the layer,
Second conductive layer made of AlGaInP formed on the active layer
And a second conductive type clad layer.
Second conductive type electrode in ohmic contact via cap layer
And a visible light semiconductor light emitting device. 4. The method according to claim 1, wherein the [ 100 ] plane of the GaAs substrate is [01]
1] on a plane inclined by 5 ° or more in the direction.
Buffer layer and an active layer made of AlGaInP.
The AlGaInP-based semiconductor layer is decompressed MOCV in this order.
Visible semiconductor light emission characterized by being formed by method D
Device manufacturing method. 5. The method according to claim 1, wherein the [ 100 ] plane of the GaAs substrate is [01]
1] on a plane inclined by 5 ° or more in the direction.
Buffer layer, first cladding made of AlGaInP
Layer, active layer made of AlGaInP, AlGaInP
The second cladding layer is formed in this order by the reduced pressure MOCVD method.
Visible light semiconductor light emitting device characterized by being formed by
Manufacturing method.