JPH0521843A - Semiconductor material having single heterojunction - Google Patents

Abstract

PURPOSE:To provide a material for a semiconductor element such as a high luminance LED, LD, etc., having a high luminous efficiency, an excellent current diffusion. CONSTITUTION:An n-type Te-doped GaAsP active layer 4 and a p-type Zn-doped GaInP clad layer 5 are formed on an n-type GaAsP substrate 3'. The surface of the layer 4 becomes flat, and low dislocation density. Ohmic properties between the layer 5 and an electrode are improved. Since the clad layer of a thick film can be grown by a liquid growth, a thickness from the electrode to a p-n junction can be sufficiently obtained as a current diffused layer. Since Zn dopant has a large diffusion coefficient, the p-n junction is formed at the inside of the substrate having more excellent crystallinity than that of the surface to improve electric characteristics, and high luminance can be expected.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a direct transition type III-V
Light-emitting diode (LED) made of group-based semiconductor crystal material
And materials for semiconductor devices such as semiconductor lasers (LD).

[0002]

2. Description of the Related Art As an LED that emits red to green light, there is, for example, a homojunction LED as shown in FIG. In this homojunction LED, n-type GaAs or GaP substrate 10
A GaAsP layer 101 is vapor-phase-grown on 0, and a pn junction is formed by doping the dopant by a method such as diffusion or ion implantation.

[0003]

By the way, the thickness of the p-type GaAsP layer 102 inverted by doping (that is, the distance from the electrode to the pn junction interface) is determined from the viewpoint of current diffusivity.
It is preferably about 25 to 45 μm. However, vapor diffusion,
With the method such as ion implantation, the limit is about 3 to 5 μm, and it is difficult to secure the above film thickness. Therefore, the current diffusivity deteriorates, and light is emitted only in the vicinity of the electrodes, which causes a decrease in brightness. Further, since vapor phase diffusion is performed under high temperature conditions, it is necessary to prevent the V group element from scattering due to heat, but it is difficult to control the vapor pressure of the V group element. On the other hand, since the ion implantation can be performed under low temperature conditions, it is relatively easy to control the vapor pressure of the group V element, but there are unavoidable problems such as high cost and deterioration of crystallinity due to ion implantation.

Further, even if the vapor pressure of the group V element is optimized and diffused to form a good pn junction, p
Since the p-type GaAsP layer 102 on the n-junction serves as an absorption layer for light emission, the light obtained from the light emission (active) layer could not be efficiently extracted to the outside. At the same time, as long as the internal quantum efficiency is homojunction, there is a limit to the improvement in efficiency, and it is not possible to expect high brightness. Considering the above facts,
An object of the present invention is to provide a material for a semiconductor device such as a high-brightness LED or LD which has high luminous efficiency and good current diffusion.

[0005]

As a result of earnest research to achieve the above object, the present inventors have developed the following semiconductor materials. That is, the semiconductor material of the present invention is GaP or
It is characterized in that at least a GaAsP-based layer and an AlGaP or GaInP-based layer are sequentially formed on a GaAs substrate. Among them, a preferred embodiment is GaP or Ga.
At least a GaAsP active layer and a dopant-containing GaInP clad layer are sequentially formed on an As substrate, Ga
An N- or O-doped GaP active layer and a dopant-containing AlGaP clad layer are formed at least sequentially on a P substrate, and the dopant of the clad layer is a Zn dopant.

The GaAsP-based layer means GaAs _x P _1-x (0 < x <
It means a mixed crystal having a constant composition represented by 1) and can be an active (light emitting) layer. When the GaAsP-based layer is an indirect transition region, a dopant such as N or O is contained as an isoelectronic center to form an active (light emitting) layer.

A GaAsP composition gradient layer for relaxing lattice mismatch may be interposed between the GaAsP-based layer and the substrate. The GaAsP compositionally graded layer, for example, grows on a GaP substrate from a mixed crystal with a high GaP mole fraction to a gradually lower mixed crystal, and in the case of a GaAs substrate, on the contrary, with a GaP mole fraction. It is formed by growing a layer having a stepwise multi-layer structure or a continuous composition gradient structure from a mixed crystal having a low rate to a mixed crystal having a gradually higher rate. A GaAsP substrate in which a GaAsP composition gradient layer and a GaAsP constant composition layer are sequentially grown on a GaP substrate is commercially available, and a GaAsP active layer may be further grown on this GaAsP substrate. The GaAsP-based layer can also be used as the active layer.

As a method for epitaxially growing a GaAsP compositionally graded layer and a GaAsP-based layer, conventionally known vapor phase growth (chloride method, halide method), MOVPE (organic metal vapor phase epitaxial growth method), MBE (molecular beam epitaxial growth method), LPE. (Liquid phase epitaxial growth method)
The method may be selected from among the methods described above, and the yo-yo solute supply method (see JP-A-63-81989 and Japanese Patent Application No. 2-80330) may also be used for growth.

The AlGaP-based layer means Al _y Ga _1-y P (0 <y <
The GaInP-based layer is a mixed crystal with a constant composition represented by 1)
_It means a mixed crystal having a constant composition represented by _z In _{1 -z} P (0 <z <1), and each can serve as a cladding layer. Al
The mixed crystal composition of the GaP and GaInP-based layers is adjusted so as to be lattice-matched with the GaAsP-based layers. A specific mixed crystal composition is, for example,
In the case of a GaInP-based layer, it is 0.50 to 1.0 when expressed by the mole fraction of GaP.
0, preferably 0.51 to 1.00, more preferably 0.60 to 0.95
Is. The GaP mole fraction is selected according to the desired emission wavelength.

In the semiconductor material of the present invention, the GaAsP-based layer may be the active layer, the AlGaP and GaInP-based layers may be the cladding layers, and the heterojunction interface thereof may be the pn junction interface. Therefore, the distance from the electrode to the pn junction interface (which may be equal to the thickness of the clad layer) may be 25 μm or more in order to improve the current diffusivity, which depends on the yo-yo solute supply method described above. For example, it can be 100 μm. However, in the case of normal LPE, it is 45 in one growth.
The limit is about 25 μm, and if the film is too thick, it may absorb luminescence, so it is 25 to 45 μm, preferably 30 to 40 μm.
It is suitable to set the thickness to about μm. For the above reasons, AlGa
Since the P and GaInP-based layers need to be grown relatively thick, the growth method of the AlGaP or GaInP-based layer is preferably LPE, which facilitates thick film growth.

When an AlGaP or GaInP-based layer is grown on a GaAsP-based layer, a GaAsP that is in equilibrium with the GaAsP-based layer in order to improve the surface morphology due to the GaAs or GaP substrate.
It is desirable to grow the AlGaP or GaInP-based layer after performing liquid phase growth using a system growth solution. By performing this treatment, the interface of the heterojunction becomes flat and the electrical characteristics are improved.

The GaInP-based layer usually contains In as a solvent and is mixed with an appropriate dopant, and further contains Ga and InP or GaP and In.
A solution containing P can be prepared, and this solution can be sequentially grown on the substrate by a known means. At this time, In
As described above, the amount of InP and GaP or Ga and GaP added to the solvent is such that the mixed crystal composition of the GaInP-based growth layer precipitated from these solutions is 0.50 to 1.00 in terms of GaP mole fraction, preferably
It may be 0.51 to 1.00, and more preferably 0.60 to 0.95.

It is desirable that a dopant is mixed in the GaAsP, AlGaP and GaInP based layers, and Se and
Te, S, etc. are 5 × 10 ^{16 to} 5 × 10 ¹⁹ cm ^-3 , and AlGaP and GaInP-based layers are Zn, Be etc. 5 × 10 ^{16 to} 5 × 10 ¹⁸ cm ^-3.
Dope to a degree.

By the way, AlGaP or Ga is formed on the GaAsP-based layer.
When growing an InP-based layer, As or P is dissociated at the interface of the GaAsP-based layer due to the temperature increase until the start of growth and the heating during the homogenization of the growth solution. )
There is concern about deterioration of crystallinity. Therefore, AlGaP or Ga
Zn is contained as a dopant in the growth solution of the InP-based layer. Since the Zn dopant generally has a large diffusion coefficient, it diffuses into the GaAsP-based layer during growth, and the pn junction is formed of GaAsP.
It will be formed on the substrate side by about 2 to 3 μm from the surface of the system layer. The inside of the GaAsP-based layer in which the pn junction is formed has better crystallinity than the surface, so that improvement in electrical characteristics and high brightness can be expected as a result. Therefore, AlGaP and GaIn
It is particularly desirable to dope the P-based layer with Zn.

[0015]

The semiconductor material according to the present invention will be described in detail below with reference to the drawings. FIG. 1 shows the structure of the semiconductor material of the present invention in which an n-type GaAsP-based active layer 4 and a p-type GaInP-based cladding layer 5 are grown on an n-type GaAsP-based substrate 3 '.
FIG. 3 shows a schematic sectional view of a crystal growth apparatus used when manufacturing the material of the present invention.

The n-type GaAsP-based substrate 3'is (100) or (1
On the GaP (or GaAs) substrate 1 having the plane orientation of 11), a GaAsP composition gradient layer 2 and a GaAsP constant composition layer 3 having a mixed crystal composition of 0.70 to 0.05 in terms of GaP mole fraction are grown. Yes, the mixed crystal ratio of the GaAsP-based constant composition layer 3 is
It is uniquely determined from the composition that lattice-matches the composition of the P-based active layer 4.

Using this n-type GaAsP substrate 3 ', an n-type Te-doped GaAsP active layer 4 (hereinafter also referred to simply as "active layer") and a p-type Zn-doped GaInP clad layer 5 (hereinafter simply referred to as "clad" are formed by a slide board method. Also referred to as "layer").

The slider 13 of the crystal growth apparatus as shown in FIG.
Then, the GaAsP substrate 3'is set. And a certain amount of Ga, GaAs, Ga cleaned by chemical etching and cleaning
P and Te are inserted into the solution reservoir 11a of the slide boat 10. Similarly, a predetermined amount of In, InP, GaP and Zn is inserted into the solution reservoir 11b. As a material to be inserted into the solution reservoirs 11a and 11b, Ga-As-P-Te and In-Ga-P-Zn alloys which have been sufficiently mixed in advance by an appropriate method may be used.

To give a concrete example of the charged amount, in the n-type Te-doped GaAsP active layer 4, GaAs 2 is added to Ga 3 g.
38.8mg, GaP42.8mg, Te 0.01-0.1mg, p-type Zn doping
In the GaInP clad layer 5, InP 8 with respect to In 3 g
Charge 2.8 mg, GaP4 2.4 mg, and Zn 0.01-0.1 mg. After inserting these materials into the respective solution reservoirs 11a and 11b, a lid 16 is provided to prevent the volatilization of phosphorus and the like.
Install on 11b.

The slide boat 10 is installed in a quartz tube 15 through which high-purity hydrogen purified by a suitable method such as permeation of a palladium membrane or an inert gas such as high-purity nitrogen or argon is passed. After sufficiently passing the above gas so that residual oxygen or water vapor does not exist in the quartz tube 15, the growth material is heated to a temperature slightly higher than the growth temperature of each layer by the electric furnace 12, for example, about 2 to 20 ° C. higher. Heating and at that temperature for a certain period of time (for example 2 to
By homogenizing each growth solution for 4 hours.

Thereafter, the growth start temperature of the active layer, for example,
Gradually cool to 820 ° C at an appropriate rate of 0.01 to 2.0 ° C / min. At this time, the Ga solution for growth of the active layer 4 is prepared so that the GaAsP is in a saturated or supersaturated state close to saturation. After that, the slider operating rod 17
To move the slider 13 to collect the solution on the GaAsP substrate 3 '.
11A, the growth solution in the solution reservoir 11a and GaAs
The P substrate 3'is brought into contact.

The solution should be at a suitable rate, for example 0.01-2.0 ° C /
Since it is gradually cooled by a minute, GaAsP becomes supersaturated in the solution, which is deposited on the GaAsP substrate 3'and the n-type Te-doped GaAsP active layer 4 grows. When the active layer 4 has an appropriate thickness, for example, about 15 μm, the slider 13 is moved to move the GaAsP substrate 3'underneath the solution reservoir 11b.
The p-type Zn-doped GaInP cladding layer 5 is grown. When the thickness reaches a predetermined value, for example, about 35 μm, the slider 13 is moved again and the growth solution in the solution reservoir 11b is doped with p-type Zn.
The growth is terminated by separating the GaInP clad layer 5 from the surface so that they do not come into contact with each other.

In the above embodiment, the GaAsP substrate 3 '
The active layer 4 is grown using a GaAsP-based growth solution that is in equilibrium with the GaAsP-based constant composition layer 3 on the surface, which makes the interface of the heterojunction flat and improves the electrical characteristics.

As a modified embodiment, as shown in FIG.
It is also possible to adopt a structure in which only the p-type Zn-doped GaInP cladding layer 5 is directly grown on the P substrate 3 ', that is, a structure in which the GaAsP-based constant composition layer 3 serves as an active layer. This embodiment has the advantage that only one growth step is required.

In the above-mentioned embodiments, since the Zn dopant of the cladding layer 5 generally has a large diffusion coefficient, GaAs is not grown during the growth.
Diffuses in the P system layer. For example, the GaAsP constant composition layer 3 in FIG.
The Zn dopant is diffused into (near the surface of the GaAsP substrate 3 ') to form the p-type Zn-doped GaAsP active layer 6. GaAsP
Since the pn junction is formed on the inner side of the substrate having better crystallinity than the surface of the substrate 3 ', improvement in electrical characteristics and high brightness can be expected. Further, the diffusion of the Zn dopant by the liquid phase growth method has better crystallinity than that by the vapor phase growth method.

In the present invention, the wavelength region can be reduced by arbitrarily selecting the mixed crystal ratio (x) of the GaAsP-based layer as the active layer.
Although visible light of 555 to 700 nm can be obtained, when x is 0, the GaInP layer is unsuitable as a cladding layer.
As shown in, the AlGaP layer is used as the cladding layer.

In the above-mentioned embodiments, the case where the (100) plane or the (111) plane of GaAsP is used as the seed crystal substrate has been described, but any other plane can be used. Further, although it may be an off substrate or a just substrate, it is desirable that the substrate having an off angle of 1 to 5 has a better surface morphology.

[0028]

Since the semiconductor material of the present invention is constructed as described above, it has the following effects.
Since it is easy to grow the AlGaP and GaInP-based layers thick by liquid phase growth, the distance from the electrode to the pn junction interface can be adjusted to improve the current diffusivity, which in turn enables higher brightness. . Further, in the heterostructure, since AlGaP and GaInP mixed crystals having a bandgap larger than the emission wavelength are used as the surface (cladding) layer, the emission from the active layer is not absorbed and the injection rate is high, resulting in higher brightness. I can hope.

Particularly, in the case where the cladding layer is doped with Zn, the pn junction is formed inside the GaAsP substrate having better crystallinity than the heterojunction interface, and the electrical characteristics are improved in addition to the high brightness. Can be expected.

In addition, it is possible to increase the concentration of the dopant and reduce the contact resistance between the GaInP epitaxial layer and the electrode. Therefore, when an LED or LD is manufactured by providing an electrode on the semiconductor material of the present invention, the adhesion and ohmic property of the electrode are good, and the performance and reliability can be remarkably improved.

Further, by properly selecting the mixed crystal ratio of the GaAsP substrate, substrates having a wide variety of lattice constants can be manufactured and applied to various uses.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a semiconductor device material according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of a crystal growth apparatus used when manufacturing the material of the present invention.

FIG. 3 is a sectional view of a semiconductor device material according to a modified embodiment.

FIG. 4 is a sectional view of a semiconductor device material according to a modified embodiment.

FIG. 5 is a cross-sectional view of a conventional homojunction type LED.

[Explanation of symbols]

1: n-type GaP substrate 2: n-type GaAsP composition gradient layer 3: n-type GaAsP constant composition layer 3 ': n-type GaAsP substrate 4: n-type Te-doped GaAsP active layer 5: p-type Zn-doped GaInP cladding layer 6: p Type Zn-doped GaAsP active layer 10: Slide boats 11a, 11b, 11c: Solution reservoir 12: Electric furnace 13: Slider 15: Quartz tube 16: Lid 17: Slider operating rod

Claims (4)

[Claims] 1. At least Ga on a GaP or GaAs substrate.
A semiconductor material in which an AsP-based layer and an AlGaP or GaInP-based layer are sequentially formed. 2. At least a dopant-containing GaAsP active layer and a dopant-containing GaInP on a GaP or GaAs substrate.
The semiconductor material according to claim 1, wherein the clad layers are sequentially formed. 3. The semiconductor material according to claim 1, wherein an N or O-doped GaP active layer and a dopant-containing AlGaP clad layer are formed at least sequentially on a GaP substrate. 4. The dopant contained in the cladding layer is
The semiconductor material according to claim 2, which is a Zn dopant.