JPH02246342A - Semiconductor device - Google Patents

Abstract

PURPOSE:To obtain an InAs system ultra high speed HEMT which is formed of epitaxial constitution free from DX center and able to generate only two-dimensional electron by introducing a third semiconductor with a suitable film thickness into the hetero interface of a second kind of hetero junction system. CONSTITUTION:Between an InAs (or containing InSb) channel 5 and a GaSb (or containing GaAs) electron supplying layer 6, a third semiconductor 7 which has a specified thickness and is composed of AlSb (or containing AlAs or GaAs) is introduced. As a result, by the third semiconductor 7 inserted into a hetero interface 4 of a second kind of hetero junction system, only two-dimensional electron is produced, and the threshold value is suitably controlled by changing the film thickness of the third semiconductor 7. Further, since the electron supplying layer 6 is a layer of GaSb (or containing GaAs), the problem of DX center is not encountered. Thereby ultra high speed HEMT (high electron mobility transistor) can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor device, and more specifically, an IIEMT device (formerly ghElect
ron Mobility Transister D
evice), relates to a semiconductor device based on an shrimp configuration that generates two-dimensional electrons.

In recent years, the high speed performance of HEMT elements has been remarkable, but on the other hand, the demand for higher speeds is unstoppable.For this reason, new materials for higher speeds are actively being discovered, and InAs-based materials with high electron speeds are actively being discovered. The performance of the materials cannot be overlooked.

[Conventional technology]

A HEMT has a structure in which an electron supply layer containing impurities that generate free electrons and a channel layer in which free electrons travel are separated. That is, undoped GaAs is placed on a semi-insulating GaAs substrate, and Sl is added to IQ"am-'
n-AlHGa+-x As (x
=0.3) using molecular beam crystal growth technology MBE (mo
The film is grown to a thickness of about 0.07 μm using regular beam epitaxy. On top of this, n-GaAs doped with the same Si is grown. n-AlGaA
The electrons emitted from the donor impurity in s are depleted by the heterojunction between the Schottky junction and GaAs, and some of them move toward the metal, and some of them cross the heterojunction and move to the GaAs side, which has lower energy, and then move laterally. A two-dimensional electron gas (20F, G) with directional freedom will be created. Since the layer containing impurity donor ions that supply electrons and the layer in which electrons travel are spatially separated, electrons can move at high speed without being affected by scattering by impurities. Here, the thickness of DEC is within about 10 nm.

In particular, the mobility of the two-dimensional electron gas becomes extremely large at low temperatures, and at 77 degrees, it becomes 20 to 30 times as high as St, and in some cases exceeds 100.000 CIJ/V, S. In HEMT devices, T is used as a Schottky gate.
i/PL/Au and Au-Qe/Au are used for the source and drain electrodes,
The source/drain current is controlled by changing the electron concentration directly under the gate using the gate electrode.

[Problem to be solved by the invention]

By the way, in order to create a device even faster than the current HEMT, we need to use rnAs (indium arsenide), which is said to have one of the fastest channels for electrons.
There is.

At present, there are no reports of HEMT devices using InAs, but by analogy with conventional technology, Al5b (aluminum antimony), which has a lattice constant close to that of InAs, is considered to be an electron supply layer when InAs is used as a channel. It will be done.

However, since this material contains a large amount of AI, doping is difficult, and problems such as DX centers are likely to occur.

Therefore, the bottleneck in realizing a HEM T device using InAs as a channel is that it does not have a DX center and what kind of material is selected for the electron supply layer.

Therefore, the present invention provides a new combination as an electron supply layer for realizing an InAs-based HEMT, which allows electrons to be easily supplied to a conduction channel made of InAs-based material, and is based on a shrimp structure without a DX center. The purpose is to provide semiconductor devices.

[Means to solve the problem]

In order to achieve the above object, the semiconductor device according to the present invention has a second type of heterojunction system having semimetallic properties in which two-dimensional electrons and two-dimensional holes are generated simultaneously, and is made of a channel layer made of an InAs-based material and a GaSb-based material. A third semiconductor layer made of an AlSb-based material having a predetermined thickness is introduced between the channel layer and the electron supply layer, and the second type of heterojunction is A semiconductor characterized in that simultaneous generation of two-dimensional electrons and two-dimensional holes in the system is suppressed to generate only two-dimensional electrons, and a threshold value is also controlled by changing the film thickness of the third semiconductor. Equipped with equipment.

[Effect]

In the present invention, an Al5b (or AlA
A third semiconductor layer is introduced, consisting of S or GaAs).

Therefore, only two-dimensional electrons are generated by the third semiconductor inserted into the heterointerface of the second type of heterojunction,
In addition, by changing the thickness of the third semiconductor, the threshold value can be appropriately controlled. Furthermore, since the electron supply layer is a GaSb (or GaAs-containing) layer, there is no concern about the DX center problem, and ultrahigh-speed HEMT can be realized.

〔Example〕

Hereinafter, the present invention will be explained based on the drawings.

Figure 1 is an explanatory diagram of the principle of the present invention, and Figure 1 (a) is a
FIG. 2 is a band diagram of a second type of heterojunction made of aSb/InAs (gallium antimony/indium arsenide). In this figure, the valence band of GaSb is
Since it is energetically above the conduction band of s, two-dimensional electron gas (20EG) and two-dimensional hole gas (20EG) are present at the Peter interface.
2DHG) is generated and becomes a semimetal state.

However, if a third semiconductor layer with a lattice constant close to that of the semiconductor material and a large band gap is inserted at the Peter interface, the electrostatic potential will be absorbed by that layer, so that As shown, it is possible to relatively change the energy levels of the valence band of aSb and the conduction band of 1nAs as appropriate. Therefore, GaSb is n
By doping the mold and selecting the thickness of the third semiconductor appropriately, only two-dimensional electrons can be generated, and the threshold value can also be freely controlled.

In the present invention, as described above (as a method of supplying electrons to InAs-based materials, it is possible to generate only two-dimensional electrons by inserting an n-type ASB (or GaAs-containing) and a third semiconductor into the hetero interface. By changing the film thickness of the third semiconductor, it is possible to realize an n-type ultra-high-speed HEMT in which the threshold value can be controlled.
(or containing GaAs), the characteristic is that there is no problem with the DX center, which has been a concern in the past.

Note that the InAs-based materials mentioned in the claims include the above-mentioned 1.
Materials containing not only nAs but also InSb may be used, and GaSb-based materials include not only the above-mentioned Ga5b but also G
It may also be a material containing aAs. Furthermore, in addition to AlSb, AlSb-based materials include, for example, AlAs or GaA.
It may be a material containing s.

Examples will be described below based on the above basic principle. Second
．． FIG. 3 is a diagram showing the first embodiment of the semiconductor device according to the present invention, in which InAs and GaS are used as the second type of heterojunction system.
This is an example using b. In Figure 2, l is HEMT
(semiconductor device), and the HEMTI has a semi-insulating substrate 2 made of GaSb and a 1-AISb (1-AISb) with a film thickness of 0.5 μm.
A buffer layer 3 consisting of an intrinsic semiconductor (aluminum/antimony) and a film thickness of 30 mm as a second type of heterojunction system 4.
1-1nAs in nm (intrinsic semiconductor - indium arsenic)
and a channel layer 5 consisting of T(3(
n-GaS doped with 2×1QIac, -3 (tellurium)
b (n-type gallium antimony); a third semiconductor layer 7 made of 1-AISb with a thickness of 10 nm introduced between the channel layer 5 and the electron supply layer 6; and a third semiconductor layer 7 with a thickness of IQ nm. a semiconductor layer 8 made of 1-AISb,
A semiconductor layer (contact layer) 9 made of 1-GaSb with a film thickness of 5 nm, a gate electrode lO made of A1, and an AuSn
Source/drain electrodes 11 and 12 made of (aluminum/tin). Here, the third semiconductor layer 7 is a heterojunction system 4 consisting of a channel layer 5 made of l-1nAs and an electron supply layer 6 made of n-Garb.
It was inserted to suppress the simultaneous generation of semimetallic two-dimensional electrons and two-dimensional holes in In
It is a semiconductor layer with a lattice constant close to that of As and GaSb and a large band gap. When the third semiconductor layer 7 is inserted, the electrostatic potential is absorbed by that layer, so as shown in FIG.
It is possible to relatively vary the energy level of the conduction band of s. Therefore, by doping GaSb to n-type and selecting an appropriate third film thickness, it is possible to generate only two-dimensional electrons and control the threshold value.
EMTI can be achieved. Furthermore, the electron supply layer is GaSb.
(or containing GaAs), the problem of the DX center, which has been a concern in the past, does not occur.

As explained above, according to this embodiment, it is possible to suppress the semimetallic characteristics observed in the second type of heterojunction system in a HEMT device using InAS as a channel, and the film of the third semiconductor layer 7 can be suppressed. The threshold value can be easily controlled by changing the thickness. Furthermore, since an n-type HEMT element 1 without a DX center can be realized, this greatly contributes to the development of ultra-high-speed elements.

FIG. 4 is a diagram showing a second embodiment of the semiconductor device according to the present invention, in which InAsSb and G
This is an example using aSbAs. In FIG. 4, 21 is a HEMT (semiconductor device), and the HEMT 21 is a GaS
a semi-insulating substrate 22 consisting of i-A I S b
o, ssA 3o, +t buffer [23 and 1-1nA 9(+, 9
ss b6. . An undoped channel layer 25 consisting of 5
and Te-doped n-
QaSbo, to *h8 (electronic supply consisting of 1,04 [2
6, the channel layer 25 and the electron supply Ff! i-A 1*, s G ao, t A So introduced during J26
, + S bo, q, and i
A semiconductor layer 28 consisting of A I S bo, ssA So, +z, i Ga S bo, qiA So,
A semiconductor layer (contact layer) 29 made of OA, a gate electrode 30 made of AI, and A u T e / A u
The source/drain electrode 3L 32 is composed of the following.

The semiconductor material of the electron supply 126 in this embodiment is n-GaS
bAs, and the semiconductor material of the third semiconductor layer 27 is i
(or lightly doped) - AIG a A S
% channel layer 25 is In5bAs.

Therefore, even in this embodiment, the same effects as in the first embodiment can be obtained.

〔Effect of the invention〕

According to the present invention, only two-dimensional electrons can be generated and the threshold value can also be controlled by introducing a third semiconductor having an appropriate thickness into the heterointerface of the second type of heterojunction system. , can easily supply electrons to the conduction channel made of lnAS-based materials. As a result, we developed an InAs-based ultra-high-speed HEM with a shrimp configuration without a DX center.
T can be realized.

[Brief explanation of drawings]

FIG. 1 is a diagram explaining the principle of the present invention, FIG. 2.3 is a diagram showing a first embodiment of a semiconductor device according to the present invention, FIG. 2 is a cross-sectional view showing its structure, and FIG. Band Diagram FIG. 4 is a sectional view showing the structure of a second embodiment of the semiconductor device according to the present invention. l, 21...HEMT (semiconductor device), 2.
22... Semi-insulating substrate, 3.23... Buffer layer, 4.24... Second type heterojunction system, 5.25
...Channel layer (channel layer made of InAs-based material), 6.26...Electron supply Jl! 1 (channel N made of GaSb-based material), 7.27...Third semiconductor layer (AI Sb
8.28... Semiconductor layer, 1O130... Schottky gate electrode, 11
~12.31~32... Source/drain electrode, 2DEG... Two-dimensional electron gas, 2D HG
・・・・・・Two-dimensional hole gas. )nAs Gasb Eζ=Es−Δ Garb is a diagram explaining the principle of the present invention. 5ul) □22 Cross-sectional view showing the structure of the second embodiment

Claims (1)

[Claims] In a second type of heterojunction system having semimetallic properties in which two-dimensional electrons and two-dimensional holes are generated simultaneously, a channel layer made of an InAs-based material and an electron supply layer made of a GaSb-based material are combined. A third semiconductor layer made of an AlSb-based material having a predetermined thickness is introduced between the channel layer and the electron supply layer, and the two-dimensional electrons in the second type of heterojunction system are A semiconductor device characterized in that simultaneous generation of two-dimensional holes is suppressed to generate only two-dimensional electrons, and a threshold value is also controlled by changing the film thickness of the third semiconductor.