JPH01223720A - Semiconductor device - Google Patents

Abstract

PURPOSE:To minimize an effect oil the deterioration of the performance of a semiconductor element of various crystal defects existing in high density in a crystal layer, and to improve the performance and reliability of the element, by using the crystal layer, in which micro spinodal decomposition is generated, as a hetero-epitaxial growth layer formed onto a substrate of a different kind. CONSTITUTION:An N-type GaAs layer 2 is formed on a face (100) N-type silicon substrate 1 through a normal-pressure MOVPE method, the surface of the silicon substrate 1 is thermally treated in a hydrogen atmosphere and cleaned, and an amorphous layer in approximately 100Angstrom is formed at a temperature of approximately 450 deg.C. An N-type InGaP layer 3 approximately lattice-matching with GaAs and a P-type InGaP layer 4 are grown onto the GaAs layer through a hydride VPE method. A crystal layer in the InGaP layer generates micro spinodal decomposition, and dislocation in a crystal is difficult to be moved. Accordingly, an ohmic electrode 5 composed of an Au-Zn-Ni alloy, etc., is shaped onto the surface of P-type InGaP acquired, and a mesa type light-emitting diode including the electrode 5 is formed.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an economical and highly reliable semiconductor device.
In particular, it relates to a semiconductor device in which the crystal layer is an epitaxially grown crystal of the group ■-■ or group I[-VI that undergoes spinodal decomposition.

[Prior art]

The technology for epitaxially growing compound semiconductors such as GaAs on silicon (Si) substrates has been actively researched for the following reasons: (1) it can be easily grown into a large area, and (2) it can be expected to be inexpensive. It is being said.

It has become clear from many research results that a fairly high-quality single crystal thin film can be obtained, and GaAs F
E T (Field Effect Transi
stor).

GaAs/GaAlAs HB T (Heteroj
unction Bipolar Transist
or), GaAs/GaAlAs lasers, etc. have been manufactured.

[Problem to be solved by the invention]

However, the characteristics and reliability of these devices are still at an extremely insufficient stage. The biggest reason for this is the mismatch between the lattice constant and thermal expansion coefficient between the silicon (Si) substrate and the compound semiconductor layer. Taking GaAs/SL as an example, there is a difference of about 4 percent in lattice constant and about 60 percent in thermal expansion coefficient.

This causes Ga As on Si to have 10'
It has been revealed that crystal defects such as dislocations exist at a high density of /cm°2 to 10"/am-", and that tensile stress of about 10'dynas/a# exists.

These defects and stresses have a significant impact on device characteristics and reliability. In FETs, variations in pinch-off voltage or threshold voltage occur, and in HBTs and laser diodes, characteristics rapidly deteriorate. For example, GaAIAS/GaA
It is clear that even the best-performing S laser reported has a lifetime of only about 4 hours when operated continuously.

Therefore, it has been reported that it is effective to form so-called buffer layers of various structures between the Si substrate and the compound semiconductor layer in order to reduce defects and stress. In particular, a so-called superlattice buffer layer, which is a stack of two or more extremely thin semiconductor crystal layers with different lattice constants, is said to be the most promising.

However, even if these latest technologies are used, it is considered extremely difficult to reduce the density of crystal defects to the 1050-2 range.

Even in the combination of the same ■-■ group or II-VI group, if lattice matching cannot be achieved, a high density of crystal defects will occur, and a buffer layer with a complex structure is required for practical device fabrication. It is expected that

On the other hand, technology for forming a semiconductor single crystal layer on an amorphous insulating substrate such as glass is also important for application.

In particular, it is easy to separate elements, which is advantageous for forming high-speed integrated circuits, and research is also being carried out to increase the area and make it three-dimensional. In this case, it is common to first form an easily crystallized intermediate layer such as germanium (Ge) on an amorphous substrate, and then perform epitaxial growth of ■-v group, ■-■ group, etc. Therefore, rare crystal defects are introduced into the epitaxial layer at a density similar to or higher than that on the Si substrate. And it is even more difficult to reduce the density than on a Si substrate.

As described above, in the technique of epitaxially growing a semiconductor crystal on a heterogeneous substrate and using it for device fabrication, the most important issue has been to reduce the influence of crystal defects in the epitaxial layer.

In particular, conventional research has focused on methods of reducing defect density itself, which has faced great difficulties.

The present invention has been made to solve the above-mentioned problems.

An object of the present invention is to provide a technology that can improve the performance and reliability of a semiconductor device using a so-called heteroepitaxial growth layer on a different type of substrate, without worrying about reducing the crystal defect density in the epitaxial layer. It's about doing.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Means to solve the problem]

A brief overview of typical inventions disclosed in this application is as follows.

The present invention is directed to crystals of ■-■ group and If-
This is a semiconductor device provided with a group VI crystal, and the most important feature is that the epitaxially grown group 1-V or group II-2 crystal is a crystal layer in which spinodal decomposition occurs.

In addition, ■−■
The present invention is a semiconductor device provided with a group or n-VI group crystal, and is characterized in that the epitaxially grown group 1-2 or n-VI group crystal is a crystal layer in which spinodal decomposition occurs.

That is, the present invention seeks to apply the useful properties caused by spinodal decomposition to heteroepitaxial growth on silicon substrates, etc., regardless of the growth method.
This is different from the conventional idea of simply trying to reduce the dislocation density.

Of course, applying the present invention under conditions of low dislocation density will produce even more useful results.

[Effect]

According to the above-mentioned method, by using a crystal layer in which microscopic spinodal decomposition has occurred as a heteroepitaxial growth layer formed on a heterogeneous substrate, various crystal defects present at high density in the crystal layer can reduce the performance of the device. The impact on the environment can be minimized.

Spinodal decomposition is a compositional fluctuation that occurs in a solid solution with a composition in the unstable region of mixing that does not require critical nucleation. If spinodal decomposition is used, l in a solid can be
O angstrom (person) to 10 micrometer (
It is possible to form a region of regular compositional variation with a size of the order of .mu.m. In this case, the amount of variation in composition is a few percent
Often. Such a structure causes a regular stress distribution in the solid, thereby inhibiting the movement of dislocations in the solid.

Therefore, a solid in which spinodal decomposition has occurred becomes difficult to deform, and it is a well-known fact that various useful alloys have been developed in the field of metallurgy by taking advantage of this fact. As already mentioned, it is difficult to avoid the presence of a certain degree of high density dislocations in the (1)-V group high crystal grown on a silicon substrate. Therefore, it is practically important to acknowledge the existence of dislocations and to take precautions to prevent the dislocations from leading to deterioration in device performance.

In laser diodes and light emitting diodes, dislocations existing in the crystal multiply due to the action of current flowing through the device.
It becomes a non-luminous center and its characteristics deteriorate. It is conceivable that if these devices are manufactured using crystals in which spinodal decomposition has occurred, devices that are less susceptible to deterioration will be obtained. There have been previous attempts to link the fact that semiconductor lasers with an active layer of InGaAsP, which is lattice-matched to InP, from being easily degraded to spinodal decomposition (for example, S, Mahajanet et al.
al.

Journal of Crystal Growth
Vol, 68 pp, 589-595 (1984))
There is no example in which this idea has been applied to a crystal material with an extremely large lattice mismatch, such as m-v group growth on silicon. The present invention is based on the fact that it has been demonstrated that the use of crystals in which spinodal decomposition has occurred is extremely effective in such cases.

The stability of mixed crystals of groups 1-2 and If-VI depends on the constituent components, but most of the mixed crystals have mixing instability at low temperatures. Therefore, it is known that the same material can be obtained in very different states depending on the method of crystal growth. For example, even if grown at the same temperature, M B E (Molecular Beam E p
itaxy) method and MOV P E (Metalor
Ganic Vapor Phase Epitaxy
) method, decomposition is less likely to occur, and liquid phase growth method and V P
Decomposition easily occurs in the E (vapor phase θE pitaxy) method, and even materials formed uniformly at high temperatures will decompose if annealed at low temperatures where mixing becomes unstable.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described in detail using the drawings.

FIG. 1 is a sectional view of a main part for explaining the outline and structure of an embodiment in which the present invention is applied to a mesa-shaped light emitting diode.

In FIG. 1, 1 is an n-type silicon (Si) substrate.

2 is an n-type GaAs layer, 3 is an n-type InGaP layer, 4
5 is a p-type InGaP layer, 5 is an ohmic electrode made of an Au-Zn-Ni alloy, and 6 is an ohmic electrode made of an Au-Ge-Ni alloy.

Ternary mixed crystal InGaP can be thought of as having InP and GaP as constituent elements, and is lattice matched to GaAs at compositions around InO, 5GaO, and sP, and its band gap is about 1.9 eV, so it is It is an important material as a visible luminescent material around 6600 angstroms. Continuous oscillation at room temperature has already been achieved in a laser diode using this material in its active layer, and the prospects for its reliability are quite promising.

On the other hand, when viewed as a mixed crystal, the lattice constants of InP and GaP differ by approximately 7%, and it is therefore expected that a wide region of unstable mixing exists.

As shown in FIG. 1, the light emitting diode of this example has (
100) surface n-type silicone (Si) group@1 (carrier density 2 x 10" (!1-3)
It is formed to a thickness of approximately 100 μm. A so-called two-step growth method is adopted for the growth, in which the surface of the silicon substrate 1 is cleaned by heat treatment at a temperature of 950°C for 15 minutes in a hydrogen atmosphere, and then a 100 angstrom (person) layer is grown at a temperature of about 450°C. An amorphous layer is formed. After this is heat treated at a temperature of about 650° C., a single crystal GaAs layer is formed thereon to a thickness of about 3 μm. This GaAs layer is doped with silicon using silane gas, and has a carrier density of about I x 10''■-1 n
formed into a shape. On this GaAs layer, an n-type InGa2 layer 3 and a p-type InGaP layer 4, which are approximately lattice matched to GaAs, are grown to a total thickness of about 2 μm by the hydride VPE method. In growing the n-type InGaPM3 and P-carved nGaP layer 4, the initial growth thickness of about 0.5 μm is doped with selenium and is an n-type I layer with a carrier density of about 7 x 10"01-3.
An nGaP layer 3 is formed and then grown with a thickness of 1°5μ.
A p-type InGaP layer 4 doped with zinc and having a carrier density of about 3.times.10"cxm-' is formed to a thickness of about 1.5m.

Note that the thickness of the n-type InGaP layer 3 is 0.3 μm, p
This is possible even when the thickness of the InGaP layer 4 is about 1.0 μm. Further, the growth temperature of InGaP was set in a range of 640°C to 690°C. The growth rate is approximately 1 μm/hour (h
our).

on the surface of the p-type InGaP thus obtained.

An ohmic electrode 5 made of an Au-Zn-Ni alloy with a thickness of about 100 μm in diameter is formed, and further a mesa-shaped light emitting diode with a thickness of about 120 to 400 μm in diameter including this ohmic electrode 5 is formed.

On the back side of the silicon (Si) substrate 1, Au-Ge-Ni
An ohmic electrode 6 made of an alloy is formed.

In addition, Figure 2 shows the results of measuring the light output characteristics using an integrating sphere when a forward current is passed through the mesa-shaped light emitting diode of this example (current vs. light output characteristics, and the peak wavelength of the spectrum is 6600 angstroms). The quantum efficiency of this mesa-shaped light emitting diode is approximately 0.3%.

In addition, the experimental results of the change over time in the optical output of the mesa type light emitting diode of this example are shown in Figure 3 (current conditions were 200 mA DC and temperature 25°C). Even if a direct current is continued to flow at the current density, almost no change is observed in the optical output after 100 hours.

l Also, the InGaP layer has about 10"Ql"2
Although there are dislocations with a density of It's for a reason.

4A, 4B, and 4c are graphs showing Raman scattering spectra of InGaP layers.

This experiment was conducted at a measurement wavelength of 5145 angstroms and an optical output of 200 mW.

As shown in Figures 4A to 4C, each peak is broader (Figure 4C) compared to the spectrum when spinodal decomposition has not occurred (Figure 4A),
Alternatively, a peak with a composition close to Ga0.8 I no, 2P is observed (Figure 4B).

Furthermore, when looking at the transmission microscopic image of the InGaP layer, InGaP layer
A columnar structure of 500 to 1000 angstroms is visible in the aP layer along the thickness direction. This structure is thought to be due to spinodal decomposition occurring during growth or cooling after growth, causing minute compositional fluctuations in the film. In this example, the VPE method, which is prone to spinodal decomposition, was used. In the MBE method or the MOVPE method, a crystal layer in which spinodal decomposition has occurred can be obtained by annealing at an appropriate temperature after growth. The magnitude of the compositional variation in InGaP according to this example is thought to be 4 to 5%, but the existence of such a minute compositional variation region has no effect on the optical and electrical properties of the crystal.

As can be seen from the above description, according to this embodiment, in the device application of the heteroepitaxial layer on the n-type silicon substrate 1, a complex structure such as a superlattice structure is used to reduce crystal defects as in the past. It is possible to provide a means for realizing a highly reliable element without using a special structure.

Moreover, this simplifies the growth method and improves economic efficiency.

The present invention has been specifically explained above based on examples, but
It goes without saying that the present invention is not limited to the embodiments described above, and can be modified in various ways without departing from the spirit thereof.

For example, although InGaP was described in the embodiment, the present invention can of course be applied to various other mixed crystal materials.

〔Effect of the invention〕

As explained above, according to the present invention, by using a crystal layer in which microscopic spinodal decomposition has occurred as a heteroepitaxial growth layer formed on a heterogeneous substrate, various crystals present in a high density in the crystal layer can be used. Since the influence of defects on performance deterioration of the device can be minimized, it is possible to improve the performance and reliability of a semiconductor device using a heteroepitaxially grown layer on a different type of substrate.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a main part for explaining the schematic configuration of an embodiment in which the present invention is applied to a mesa-type light emitting diode, and FIG. The light output characteristics when flowing with an integrating sphere i1+! 3 is a graph showing the experimental results of the optical output of the mesa diode shown in FIG. It is a graph showing a Raman scattering spectrum. In the figure, 1...n-type silicon (Si) substrate, 2...n-type GaAs layer, 3-n-type InGaP layer, 4-p-type InG
aP layer, 5...ohmic ti made of Au-Zn-Ni alloy, 6... ohmic electrode made of Au-Ge-Ni alloy.

Claims (2)

[Claims] (1) A semiconductor device in which a III-V group or II-VI group crystal epitaxially grown is provided on a silicon, III-V group crystal, II-VI group crystal substrate, and the epitaxially grown III-V group crystal is provided. A semiconductor device characterized in that the crystal layer includes a group II-VI crystal and spinodal decomposition. (2) III- grown epitaxially on an amorphous substrate such as glass or ceramic through an intermediate layer such as germanium
1. A semiconductor device including a group V or group II-VI crystal, characterized in that the epitaxially grown group III-V or group II-VI crystal is a crystal layer in which spinodal decomposition occurs.