JPS5984417A - Iii-v family mixed crystalline semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a deposited layer with few displacement by a method wherein a graded layer, whose composition changes step by step or continuously, is formed on a III-V family semiconductor substrate and a III-V family layer, which has a lattice constant different from that of the substrate, is formed on the graded layer by epitaxial growth and at that time a mixed crystalline epitaxial layer of III-V family of more than four components is used as the graded layer. CONSTITUTION:A growing chamber of a growing equipment is divided into an upper level 1 and a lower level 2 and a substrate holder 4 which is bent and to which a GaAs substrate 3 is attached is provided to the outlet side of the growing chamber so as to be rotated freely. Thus, the holder 4 is rotated and the substrate 3 is faced against the outlet side of the upper level 1 or the lower level 2. Then, using the upper level 1, AsH3 gas is introduced through an inlet pipe 5 into the upper level 1 and the temperature is risen and onto an In source 6 and Ga source 7 of the lower level 2, HCl gas is introduced and through the inlet pipe AaH3-PH3 gas is introduced and growing condition of InGaAsP mixed crystal growth is determined. After that, AsH3, PH3 are introduced onto an In source 8 and Ga source 9 in the upper level 2 and a deposition layer overlapped on the previous layer is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION In the vapor phase epitaxial growth of a 1■-V group mixed crystal semiconductor, when an epitaxial layer is grown whose lattice constant is different from that of a substrate, the lattice constant of the substrate is first matched to that of the substrate. The present invention relates to a graded layer in which the lattice constant can be changed by gradually changing the mixed crystal composition, and finally a mixed crystal having a desired lattice constant can be obtained.

In III-V group mixed crystal semiconductors, for example, In-G
In the a-As-P system, the forbidden band width FiInAs is 0.
By changing the composition, it is possible to create mixed crystals with various forbidden band widths, from 36 eV to 2.25 eV for GaP.
It can be used in a wide range of applications as optical devices such as light emitting diodes and photodetectors1. However, bulk crystals that serve as substrates are extremely difficult to fabricate using materials other than binary compounds of InP, GaAs, GaP, and InAs. Therefore, the epitaxial layer thereon has also been limited to crystals having a composition matching the lattice constant of these substrates. 4 mentioned above
In terms of elemental mixed crystals, the forbidden band width is limited to 0.75 eV to 1.28 eV when using an InP substrate, and 1.43 eV to 1.88 eV when using a GaAs substrate. become.

A technique that has made it possible to expand this range using conventionally easily available substrates is the introduction of graded layers. In other words, if a crystal whose lattice constant is significantly different from that of the substrate is grown on a substrate, a large number of dislocations will be introduced from the interface, the crystallinity will be greatly impaired, and the surface condition will deteriorate, making it difficult to obtain a practical crystal. No lips. However, when the difference in lattice constant is extremely small (Δa/a<5X10,
Δa: Difference between the lattice constant of the substrate and the lattice constant of the crystal to be grown on it; a: Lattice constant of the substrate) takes advantage of the fact that an epitaxial layer with good specularity is grown with relatively few introductions of dislocations. By changing the composition of the mixed crystal in the growth direction of the epitaxial/Vsial layer, the lattice constant is gradually changed, and finally an epitaxial layer having a desired lattice constant composition can be grown. Also, in the vicinity of , the lattice constant does not change continuously in the growth direction (
, a method of changing stepwise has been attempted. this is,
The lattice constant is changed stepwise to the extent that misfit dislocations are introduced at the interface. According to this method, if the degree of misfit is appropriate, the introduced misfit dislocations will remain within the interface and the epitaxial layer The dislocations are not propagated in the growth direction (and even some of the dislocations that have grown from the underlying crystal can escape to the outside of the crystal at the interface. In this way, the lattice constant can be Graded layer technology, which allows high-quality epitaxial layers of different types to be grown relatively easily, is expected to have a wider range of applications in the future.

By the way, in the past, a ternary mixed crystal was used as a graded layer in which an element of group III or V group = fi was added to the constituent elements of the substrate8. For example, In
-GaAs-P system, when trying to grow an epitaxial layer with a lattice constant of 5.6λ, the substrate is GaP (lattice constant: 5.45A) as a graded layer, and GaP is injected with In or 88 A method has been used to change the lattice constant by using an added ternary mixed crystal.By the way, in the case of InGaP, the ternary mixed crystal used as the graded layer has zero misfit with the lattice of the underlying crystal. When the lattice is less than .05%, the lattice parallel to the growth plane almost matches the lattice of the underlying crystal, and elastic deformation that changes the lattice constant in the perpendicular direction (relaxes strain and prevents the growth of dislocations) However, if the misfit becomes larger than that, dislocations will occur.In general, in a ternary mixed crystal, dislocations are less likely to occur in a ternary mixed crystal than in a quaternary mixed crystal of the present invention, which will be described later. When changing the lattice constant continuously, it was necessary to change the composition very slowly, and the gas flow to be supplied had to be precisely controlled. In this method, it is necessary to intentionally introduce only misfit dislocations, but in the case of ternary mixed crystals, extremely precise control of the composition is required in order to generate only these dislocations. In reality, a considerable number of dislocations occurred in the growth direction of the epitaxial del layer.

Furthermore, the surface state of the finally obtained epitaxial layer has crosshatch and linehatch patterns due to the influence of misfit dislocations, which often poses an obstacle in device fabrication.

The object of the present invention is to eliminate such conventional drawbacks and provide a graded layer with few dislocations (an epitaxial layer with good surface condition can be formed). According to the present invention, 1) t-V group semiconductor A graded layer whose composition changes stepwise or continuously is provided on the substrate, and a III-V group mixed crystal semiconductor epitaxial layer having a lattice constant different from that of the semiconductor substrate is provided on the graded layer. A group V mixed crystal semiconductor device, characterized in that the graded layer is a quaternary or more III-V group mixed crystal semiconductor evictional layer.
An IV group mixed crystal semiconductor device is obtained.

For example, in InGaAIIP quaternary mixed crystal, when growing an epitaxial layer with a composition that has a different lattice constant from that of the underlying crystal, if the misfit is within 0.3%, dislocations will not occur (crystal with good specularity). This range is about four times larger than that of the ternary mixed crystal InGaP mentioned above.In the case of a multi-component mixed crystal, when trying to grow a crystal with a lattice constant different from that of the underlying crystal, As already mentioned, the lattice parallel to the growth plane almost matches the lattice of the underlying crystal, and the crystal grows while relaxing the strain by changing the lattice constant in the vertical direction. However, as the number of constituent elements increases, the lattice changes. It is thought that the degree of freedom in replacing elements at a point increases and it is possible to cope with larger strains.Therefore, by using a multi-component mixed crystal of quaternary or higher elements as a graded layer, it is possible to continuously change the composition. Unlike ternary mixed crystals, it is not necessary to precisely control the gas flow rate to slowly change the composition (this makes it easier to form). If you want to do this, increase the number of steps to 3.
The number can be reduced to about 174 when using an original mixed crystal, and accordingly, dislocations extending in the growth direction can also be reduced. Furthermore, when an 8-element mixed crystal is used, line hatch or cross-hatch patterns are observed on the growth surface corresponding to misfit dislocations, but by using a quaternary or higher mixed crystal, excellent specularity is obtained. A grown layer can be obtained.

Next, the present invention will be explained in detail based on examples and with reference to the drawings.

EXAMPLE An example of growing an InGaAsP grounded layer on a GaAa substrate using the present invention will be described with reference to FIGS. 1 and 2. This example uses the hydride vapor phase growth method, and a schematic diagram of the growth apparatus is shown in FIG. The upstream portion of this growth apparatus is divided into two growth chambers 1.2, each of which is capable of growing an InGaAsP-based mixed crystal. The substrate 3 is placed close to the exit of each growth chamber,
By rotating the substrate holder 4, it can be moved between growth chambers in about 1 second.

The temperature was set at 800°C for the upstream IJI group Kanaoka source part and 750°C for the substrate part. The substrate 3 is GaAs (10
After setting the reaction tube in the reaction tube using the 0) surface, AdI3 gas was supplied from the introduction tube 5 in the upper growth chamber 1 (the temperature was raised at 7).

After reaching the set temperature, the In source 6 in the lower growth chamber 2
, HCI gas on Ga source 7, A8H3 from inlet pipe 8
, PHs gas was supplied and Ino2s Gao, yt Al
Conditions were set to allow the growth of 2O,4IPo,59 mixed crystals. This is a quaternary mixed crystal that is approximately lattice matched to GaAs. The substrate is transferred to the lower growth chamber to start growth, and at the same time, the upper growth chamber 1 is filled with Ino, z5Gao, 7s Ag3.
In order to grow a quaternary mixed crystal of 41 Po, 59
The flow rates of the 1■C gas on the source 8, the Ga source 9, and the A, sH3, and PH3 gases supplied from the introduction pipe 5 are set. Ino29 (about 5 μm thick) was grown in the lower growth chamber 2.
'yao7+ A8o4. After growing the s PO59 epitaxial layer, the substrate is moved to the upper growth chamber 1. Furthermore, growth is performed in one growth chamber, and while the next growth is performed in the other growth chamber, the lattice constant changes continuously in a stepwise manner as shown in the table below. A graded layer grew to the south.

In this table, the misfit with the underlying crystal is, for example, 1
The value at layer number 5 indicates the misfit with layer number 14. Misfit dislocations are introduced at the interface due to the stepwise change in the lattice constant, and the strain is relaxed. but,
H, dislocations in the long direction were introduced into fJ, which became clear from the observation of etch pits on the long surface of substrate 1.
The GaAs used as No. 1 had an etch pit density of 2000 pits/d corresponding to dislocations, but this decreased to 700 pits/d on the surface after growth. Not only does this mean that no new dislocations are introduced, but on the contrary, it has become clear that such graded layers have the effect of reducing dislocations. Furthermore, as a result of observing the surface using an interference microscope, it was found that the surface had almost no irregularities, and the method according to the present invention is a highly useful method for forming, for example, a double hetero laser structure on this surface. It became clear that -.

In this example, the InGaAsP quaternary mixed crystal was explained as an example, but the principle is similar for mixed crystals containing other quaternary elements or more elements such as a combination of group 111 and V group. It is clear that you can get results.

In the Makomoto example, the quaternary mixed crystal was grown using the hydride vapor phase epitaxy method, but the same effect can be obtained using other growth methods such as the Mi method and the 1IIIiOcVD method.

[Brief explanation of drawings]

FIG. 1 is a diagram schematically showing a hydride vapor phase growth apparatus using a two-growth tail method used in an example of the present invention.
2 is a growth chapter divided into two parts, 3 is a substrate, -111 group temporary holder, 5.8 is A3113, P) 13 and H2 gas introduction tube, 6.81j) n source, 7.9 is Ga source number Figure 2 is a diagram showing the cross-sectional structure of the layer grown in a fruitful example; 10 is a GaAs substrate crystal, and 11 is an InGaAs layer that matches the GaAs lattice.
P epitaxial layers 12 to 15 have their lattice constants changed stepwise [Grown InGaAsP epitaxial M
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Claims (1)

[Claims] A graded layer whose composition changes in a stepwise or continuous manner is provided on a ■-V group semiconductor substrate, and a ■-V group mixed crystal semiconductor epitaxial layer having a lattice constant different from that of the semiconductor substrate is formed on the graded layer. III-V provided
A group III-V mixed crystal semiconductor device, characterized in that a quaternary or higher group III-V mixed crystal semiconductor epitaxial layer is used as the graded layer.