JPH02239660A - Semiconductor device - Google Patents

Abstract

PURPOSE:To reduce a manufacturing cost by uniformly doping In in both a GaAs layer and an AlxGa1-xAs layer to form a hetero structure having small number of deep impurity level. CONSTITUTION:A hetero is composed of a GaAs layer 2 and an AlxGa(1-x)Ga layer 3 in which Si, Sn, S or Te is doped as an impurity. The component ratio (x) of Al in the layer 3 is set to a range of 0.2<=x<=0.4, and In is doped 1-10% (at%) in the layers 2, 3. Accordingly, a hetero structure of the layers 2, 3 having small deep impurity level can be formed. As a result, when Si, etc., is doped as an impurity in the layer 3, a high electron density is obtained, and temperature dependency of its electron density is eliminated. Thus, a manufacturing cost can be reduced.

Description

[Detailed description of the invention]

[11! [Field of Industrial Application] The present invention relates to a heterostructure having a GaAs layer and an AfLGaAs layer. It relates to a compound semiconductor device having a superlattice structure or a quantum well structure, and in particular, S is added to its Afl GaAs layer.
1. This paper relates to improving the electrical characteristics of semiconductor devices doped with impurities such as Sn, S, and Te. [Summary of the Invention] The present invention relates to an improvement of a compound semiconductor device having a heterostructure, a superlattice structure, or a quantum well structure including a GaAs layer and a ^11 GaAs layer. The deep impurity level that occurs when In is doped is reduced by doping In.

[Conventional technology]

In electronic devices or optoelectronic devices using compound semiconductors, a heterostructure consisting of a GaAs layer and a ^11 GaAs layer is often used as a constituent material. The reason for this is that the bottom of the conduction band of ^j2 GaAs has higher energy as seen from the electronic system than the bottom of the conduction band of GaAs, so a step in energy occurs at the junction of these two materials. This is well known. In particular, recently high electron mobility transistors (OEMTs)
, quantum well lasers, quantum well light emitting diodes, and the like, such structures are used. However, in order to generate carriers (current carriers) in these materials, n-type impurities such as Si are added ^J! GaA
It is known that when the s region is doped, a deep impurity level (so-called DX center) is formed, and carriers, that is, electrons, do not reach a sufficient density (for example, D
．． V. Lang, R. A. Logan and Mj
aros “Trapping Character”
sticks and a Donor- Complex
(DX) model for the PersIs
tentPhotoconductivity Tra
Ppping Center in Te-Doped
AIX Gat-xAs” Physical
Review (B) vol. 19, N6.2, pp
lo15-1030 1979). Deep impurity levels do not occur in GaAs, but are generated when the A4 GaAs mixed crystal is doped with impurities such as St and Te. The density of deep impurity levels is relatively small when the ^1 component is less than 20%. In other words, mixed crystals! ．． Ga. −． When expressed as ^S, if X is 0.2 or less, there is not much of a problem. When X increases from 0.2 to 0.3, the density of deep impurity levels increases rapidly. Therefore, although it is possible to reduce the density of deep impurity levels by reducing the component ratio
The step at the bottom of the conduction band at the aAs heterointerface decreases. This step is ^j! Ga is necessary to confine the electrons generated in the GaAs layer.
Confining electrons within the As layer is a necessary condition for devices that utilize two-dimensional electron gas. Therefore, as a conventional technology, ^jl GaAs is
We replaced aAs and ^1^S with a superlattice stacked alternately to a thickness of several tens of angstroms, and created GaAs in this superlattice.
(For example, Masatake Ogawa, Toshio Baba, and Furu Mizutani, ``Increasing the electron density of compound semiconductors through superlattice structure and selective impurity doping.'' Nikkei Electronics January 14, 1985 issue pp21
3-240, or κ. Kobayashi, M.
Morita, N. Kamata and T. S
uzuki Deep Electron Traps
in AIAs- GaAs Superlatti
cesas Studied by Deep-L
evel Transient Spectroscope
y, Japan Journal Appl1ed
Physics vol. 27, No. 2 ppl92
- 195 1988). By doing this, a high electron density can be obtained without creating deep impurity levels, and the bottom of the conduction band in the effective sense of the superlattice (actually, the miniband of the superlattice) can be relatively lowered. Can be made high. By appropriately selecting the thickness ratio and period of AlAs and GaAs in this superlattice, it is possible to obtain the same band gap as the Gat-11AS mixed crystal with any desired A1 component ratio X. ．． [Problems to be Solved by the Invention] In order to fabricate the above-mentioned superlattice, GaAs and Aj! with a thickness of several tens of angstroms are required. A considerable number of layers of As must be stacked. This is a molecular beam shrimp taxi (
MBE) or metal organic vapor phase epitaxy (MOCVD)
), but the manufacturing process is quite complicated. Furthermore, crystal growth operations have become even more complex in order to avoid doping impurities into the interfaces of each layer of the superlattice. Furthermore, increasing the doping density of impurities exposes the superlattice to the risk of becoming mixed crystals due to disordering phenomena. Even if the temperature of the device rises too much during semiconductor crystal growth or during use after manufacturing, there is still a possibility that the superlattice parts will mix together due to disordering phenomena and form a mixed crystal. The present inventor discovered the following while making various semiconductor materials and measuring deep impurity levels. That is, ^
1. Ga, -xAs is doped with Si, and I
This means that doping a few percent of n reduces the density of deep impurity levels. Figure 2 shows Al o, 3 Gao. 7AS (X-0.
3) shows how the density of deep impurity levels decreases when In is doped. Characteristic curve A is the case when SI is doped so that the electron density is 1 x 10"cm-' at room temperature, and characteristic curve B is the case when SI is doped so that the electron density is 1 x 10"cm-' at room temperature.
This is the case where Si is doped so that the concentration of In is doped to 4% In. The purpose of this is to reduce deep impurity levels by utilizing the above-mentioned findings of the present inventors, and to reduce the deep impurity levels by forming a superlattice as in the conventional manufacturing process. The object of the present invention is to provide a compound semiconductor device that solves the conventional problems of complexity, complexity of crystal growth operations, and fear of superlattice mixing. [Means for solving the problems] As described above. In order to achieve this object, a first embodiment of the present invention provides a semiconductor in which a heterostructure is formed by a GaAs layer and a ^JL.Ga,-,AS layer doped with Si, Sn.S, or Te as an impurity. In the device, ^1
The component ratio X of Ai in the 1xGa, -xAs layer is set to 0.
2≦x″50.4, and the GaAs layer and Aj
2. In each of the xGa and -xAs layers, 1 to 10% (a
t%》 Characterized by doping. A second embodiment of the present invention includes a GaAs layer and 51, Sn. AJI x doped with S or Te as an impurity
In a semiconductor device having a superlattice structure composed of a Ga+-xAs layer, the component ratio X of ^1 in the AJlxGat-xAS layer is set in the range of 0.2≦x≦0.4,
and a GaAs layer ^f. Ga+-. In each AS layer
It is characterized by being doped with 1 to 10% (at%). A third embodiment of the present invention is a GaAs layer doped with Sf, Sn, S, or Te as an impurity. x
In a semiconductor device having a quantum well structure composed of a Ga+-xAs layer, an AlxGa. -x The component ratio X at 8°C in the As layer is set in the range of 0.2≦x≦0.4,
and GaAs layer and All. It is characterized in that each of the Ga and -xAs layers is doped with In at 1 to 10% (at%). [Function] According to the present invention, In is added to the GaAs layer and the AlgGal layer.
-, By uniformly doping both the AiGaAs layer and the GaAs layer with few deep impurity units.
A heterostructure of layers can be constructed, resulting in A
When the j2GaAs layer is doped with Si or the like as an impurity, a high electron density can be obtained, and the temperature dependence of the electron density can be eliminated. Therefore, when this material is applied to HEMT (high electron mobility transistor), it is possible to improve the characteristics of the element, for example, the transfer conductance G
As m increases, temperature changes in the threshold voltage vth can be suppressed. According to the present invention, deep impurity levels can be reduced simply by doping In into a car, eliminating the need for any complicated structures such as conventional superlattice structures, and significantly reducing manufacturing costs. ．． [Examples] Examples of the present invention will be described in detail below with reference to the drawings. FIG. 1(A) shows a cross section of a heterostructure in an embodiment of the compound semiconductor device of the present invention. Here, while doping 5% In on the substrate 1, Ga
Grow the As layer. On this GaAs layer 2, 51 is doped and In is doped to 5%.
ft6. =Gao, ? The AS layer 3 is grown to form a heterostructure having a heterointerface 4. AIto. sG
ao. When the yAs (Si) layer 3 is doped with 5% In, the density of deep impurity levels can be reduced by more than one order of magnitude, as described above. However, doping with In creates a mixed crystal of +l GaAs and InAs.InAs has a narrow forbidden band width of about 0.36 eV, so the bottom of the conduction band of AA GaAs is about 46 meV.
Polish. If this continues, the step difference (band offset) between the conduction band and the bottom of GaAs will decrease, and the ability to confine electrons in the GaAs layer will decrease. Therefore, in the present invention, the GaAs layer 2 is also doped with In to lower the bottom of the conduction band in advance.
．． If the In doping amount is 5%, the bottom of the conduction band can be lowered by about 35 meV, and as shown in Figure 1 (B), it is possible to create a step that is almost the same as when In is not doped. Although there is no way to directly and accurately measure the height difference experimentally, it can be determined by the following calculation. GaAs and Aj! o. 3Gao. The width of the forbidden band of yAs is 1.42 eV and 1.8 eV, respectively, and 247 meV, which is 65% of the difference of 0.38 eV, is compared to GaAs when In is not doped! o. sGao,
The width of the forbidden band of lnAs, which is the step at the bottom of the conduction band of yAs, is about 0.36 eV, and Af 6. sGao
．． Difference from that of yAs1. 72meV, which is 5% of 44eV, is due to 5% In doping^J
! o. sGao. This is the amount by which the forbidden band of yAs decreases. 4B+IeV, which is 65% of this, is In-doped Aj! . , which is the size that the bottom of the conduction band of @Ga6.7^S drops, GaAs and AJ! o.
It is now generally accepted that 1i5% of the difference in the width of the forbidden band of 3Ga6, ,^S is used as the step at the bottom of the conduction band.
In the case of GaAs, it is not clear what percentage of the width of the forbidden band corresponds to the difference in the bottom of the conduction band, but in the case of InG
In the case of a heterostructure of aAs and GaAs, GaAs and ^
j! There are reports that it is 60%, which is about the same as in the case of GaAs (for example, Ando, Toyoshima, Okamoto, Itor In
``Prototype and analysis of GaAs strained layer well resonant tunnel diode'', Institute of Electronics, Information and Communication Engineers Electronic Devices Research Group Material ED86-106 9P13-20 (1986)).
Also, since the In doping amount is about 5%, the step difference at the bottom of the conduction band can be calculated between GaAs and ^fLO. 3Gaa
, ? It can be done in the same way as the calculation for ^S, using the rule that 65% of the forbidden band width is the step at the bottom of the conduction band. Similarly, the width of the forbidden band of GaAs and 1nAs is 1. 4
The difference between 2eV and 0.36eV is 1.08aV, and 65% of this 5% is about 35meV. This is,
By doping GaAs with 5% In, the bottom of the conduction band is lowered. In the present invention, by doping both the GaAs layer and the AA GaAs layer with In, All a. sG
ao. t^S (Si) does not generate deep impurity levels,
Moreover, the energy level difference with the GaAs side can be maintained almost unchanged. There is only a slight difference in level (48meV-35+
*eV-11meV) To prevent the decrease, G
By doping an additional 2% of In on the aAs side, it is also possible to create a beta structure in which the density of impurity levels is reduced without changing the step at all. Figure 1 (^) is an example of a simple heterostructure, GaA
Quantum well structure with GaAs barrier layers placed on both sides of the s layer 2, or GaAs layer 2 and AlGaAs
Even in a superlattice structure in which layers 3 and 3 are stacked periodically, the density of deep impurity levels that create impurities such as Si can be reduced by doping In as in the case of a heterostructure. The larger the amount of In doped, the more effective it is in reducing deep impurity levels, but since the lattice constant with the substrate 1 will no longer match, it is preferable to keep it within about 10%. [Effects of the Invention] According to the present invention, In is added to the GaAs layer and the ^j! Oh Ga
By uniformly doping both p-xAs layers, an AlGaAs layer and a GaA layer with few deep impurity units can be formed.
A heterostructure of the s-layer can be constructed, and as a result,
A.I. When the GaAs layer is doped with Sl or the like as an impurity, a high electron density can be obtained, and the temperature dependence of the electron density can be eliminated. Therefore, when this material is applied to HEMT (high electron mobility transistor), it is possible to improve the characteristics of the element, for example, the transfer conductance G
It is possible to increase o and suppress temperature changes in the threshold voltage vth. According to the invention! Deep impurity levels can be reduced simply by doping n, eliminating the need for complex structures such as conventional superlattice structures, and significantly reducing manufacturing costs.

[Brief explanation of drawings]

FIG. 1(A) is a block diagram showing a configuration example of a semiconductor device having a heterostructure as an embodiment of the present invention, and FIG. 1(B) is a block diagram of the embodiment shown in FIG. 1(A). FIG. 2 is an energy level diagram showing the energy relationship at the bottom of the conduction band at the telo interface. FIG. 2 is a characteristic diagram illustrating how the density of deep impurity levels decreases when doping with In. DESCRIPTION OF SYMBOLS 1...Substrate, 2...GaAs layer, 3---AlGaAs layer, 4...Hetero interface.

Claims (1)

[Claims] 1) Al_xGa_1_-_xA doped with a GaAs layer and Si, Sn, S, or Te as impurities.
In the semiconductor device having a heterostructure formed by the GaAs layer and the Al_xGa_1_-_xAs layer, the Al component ratio x in the Al_xGa_1_-_xAs layer is set in the range of 0.2≦x≦0.4, and the Al_xGa_1_-_xAs layer is A semiconductor device characterized in that each of the semiconductor devices is doped with 1 to 10% (at%) of In. 2) Al_xGa_1_-_xA doped with GaAs layer and Si, Sn, S, or Te as impurities
In a semiconductor device having a superlattice structure constituted by the GaAs layer and the Al_xGa_1_-_xAs, the component ratio x of Al in the Al_xGa_1_-_xAs layer is set in a range of 0.2≦x≦0.4, and the GaAs layer and the Al_xGa_1_-_xAs
A semiconductor device characterized in that each of the layers is doped with 1 to 10% (at%) of In. 3) Al_xGa_1_-_xA doped with GaAs layer and Si, Sn, S, or Te as impurities
In a semiconductor device having a quantum well structure constituted by an s layer, the Al_xGa_1__xAs layer has an Al component ratio x in a range of 0.2≦x≦0.4,
and the GaAs layer and the Al_xGa_1_-_xA
A semiconductor device characterized in that each of the s-layers is doped with 1 to 10% (at%) of In.