JP2796113B2 - Semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] Regarding semiconductor devices, by providing a new combination as an electron supply layer for realizing an InAs-based HEMT, electrons can be easily supplied to a conduction channel made of an InAs-based material, And with the object of providing a semiconductor device based on an epi-structure without a DX center, a channel layer containing InAs, an electron supply layer containing GaSb and doped with impurities, and the channel layer and the electron supply layer An intermediate layer including AlSb, provided between the channel layer and the intermediate layer, wherein an interface between the channel layer and the intermediate layer suppresses generation of a two-dimensional hole gas and generates a two-dimensional electron gas. Have been.

[Industrial applications]

The present invention relates to a semiconductor device, and more particularly, to a HEMT device (High Electron Mobility T
and a semiconductor device based on an epi configuration for generating two-dimensional electrons.

Although the speed of recent HEMT devices is remarkable,
On the other hand, the demand for higher speeds does not stop. For this reason, new materials are being discovered for speeding up, and the performance of InAs-based materials having a high electron velocity cannot be overlooked.

[Conventional technology]

The HEMT has a structure in which an electron supply layer containing impurities for generating free electrons is separated from a channel layer in which the free electrons travel. That is, undoped GaAs is doped on a semi-insulating GaAs substrate, and n is further doped with Si to about 10 ¹⁷ cm ^-3.
-Al _X Ga _1-X As (x = 0.3) using molecular beam crystal growth technology MBE (mo
The thickness is grown to about 0.07 μm by lecular beam epitaxy). On this, n-GaAs doped with the same Si is grown. Electrons emitted from the donor impurity in n-AlGaAs are depleted by the heterojunction between the Schottky junction and GaAs, and partly move to the metal and partly move to the lower energy GaAs side beyond the heterojunction. , To create a two-dimensional electron gas (2DEG) with lateral degrees of freedom. Since the layer containing the impurity donor ions supplying electrons and the layer in which the electrons travel are spatially separated, the electrons can move at high speed without being affected by any scattering by the impurities.
Here, the thickness of 2DEG is within about 10 nm. Especially at low temperatures, the mobility of the two-dimensional electron gas becomes very large,
In this case, the mobility becomes 20 to 30 times that of Si, and in some cases, high mobility exceeding 100,000 cm ² / V · S. In HEMT devices, Ti / Pt / Au is used as the Schottky gate, and Au-Ce is used as the source / drain electrodes.
/ Au is used, and the source / drain current is controlled by changing the electron concentration just below the gate by the gate electrode.

[Problems to be solved by the invention]

By the way, InAs (indium arsenide), which is said to be one of the materials in which the channel through which electrons travel is the fastest, is used as a material to make a device faster than the current HEMT.

At present, there is no report of a HEMT device using InAs, but by analogy with conventional technology, for example, AlSb (aluminum antimony) having a lattice constant close to that of InAs is considered as an electron supply layer when InAs is used as a channel. Can be

However, it is considered that this material contains a large amount of Al, so that doping is difficult and problems such as a DX center are likely to occur.

Therefore, the realization of a HEMT device using InAs as a channel is realized by DX
It is considered that there is no center and what kind of material is selected for the electron supply layer is a bottleneck.

Therefore, the present invention provides a new combination as an electron supply layer for realizing an InAs-based HEMT,
It is an object of the present invention to provide a semiconductor device that can easily supply electrons to a conduction channel made of an InAs-based material and that is based on an epitaxial structure without a DX center.

[Means for solving the problem]

The semiconductor device according to the present invention achieves the above object by using InAs.
A channel layer containing GaSb, an impurity-doped electron supply layer, and an intermediate layer provided between the channel layer and the electron supply layer and containing AlSb. At the interface of the intermediate layer, there is provided a semiconductor device characterized in that generation of two-dimensional hole gas is suppressed and two-dimensional electron gas is generated.

[Action]

In the present invention, an InAs (or InSb-containing) channel layer
A third semiconductor layer made of AlSb (or containing AlAs or GaAs) is introduced as an intermediate layer between the GaSb (or containing GaAs) electron supply layer.

Therefore, the generation of two-dimensional holes (hereinafter, referred to as two-dimensional holes) is suppressed by the third semiconductor inserted into the heterointerface of the second type heterojunction, and only two-dimensional electrons are generated. Ultra-high-speed HEMT that can supply electrons to the channel layer at the same time and has no concerns about the DX center
Can be realized.

〔Example〕

 Hereinafter, the present invention will be described with reference to the drawings.

FIG. 1 is a diagram illustrating the principle of the present invention, and FIG.
FIG. 4 is a band diagram of a second type heterojunction made of GaSb / InAs (gallium antimony / indium arsenide). In this figure, since the valence band of GaSb is energetically higher than the conduction band of InAs, a two-dimensional electron gas (2DEG) and a two-dimensional hole gas (2DHG) are generated at the hetero interface, resulting in a semimetal state. .

However, when a third semiconductor layer having a large bandgap and having a lattice constant close to that of the semiconductor material is inserted into the hetero interface at the hetero interface, the electrostatic potential is absorbed by the third semiconductor layer. As shown, the energy levels of the valence band of GaSb and the conduction band of InAs can be made relatively variable as appropriate. Therefore, by doping GaSb into n-type and further appropriately selecting the thickness of the third semiconductor, only two-dimensional electrons can be generated, and the threshold can be freely controlled.

In the present invention, as described above, as a method of supplying electrons to the InAs-based material, only two-dimensional electrons can be generated by n-type GaSb (or GaAs) and a third semiconductor inserted at a hetero interface. Further, by changing the thickness of the third semiconductor, an n-type ultra-high-speed HEMT capable of controlling the threshold value can be realized. Furthermore, since the electron supply layer is a GaSb (or GaAs-containing) layer, there is no DX center problem that has been a concern in the past.

In addition, the channel layer containing InAs referred to in the claims may include not only InAs but also InSb,
Further, the electron supply layer containing GaSb may contain not only GaSb but also GaAs. Further, the intermediate layer containing AlSb may be made of a material containing, for example, AlAs or GaAs in addition to AlSb.

Hereinafter, embodiments will be described based on the above basic principle. 2 and 3 are views showing a first embodiment of the semiconductor device according to the present invention, in which InAs and GaSb are used as a second type of hetero-coupling system. In FIG. 2, reference numeral 1 denotes a HEMT (semiconductor device), and HEMT 1 is a semi-insulating substrate 2 made of GaSb;
A buffer layer 3 made of i-AlSb (intrinsic semiconductor-aluminum / antimony) having a thickness of 0.5 μm, and a 30 nm-thick i-InAs (intrinsic semiconductor)
Channel layer 5 made of indium / arsenic) and film thickness
N-Ga doped with 2 × 10 ¹⁸ cm ^-3 of Te equivalent (tellurium) at 50 nm
Electron supply layer 6 made of Sb (n-type gallium / antimony)
And a third semiconductor layer 7 of i-AlSb having a thickness of 10 nm introduced as an intermediate layer between the channel layer 5 and the electron supply layer 6.
A semiconductor layer 8 of i-AlSb with a thickness of 10 nm, and a thickness of 5 n
m, a semiconductor layer (contact layer) 9 made of i-GaSb;
and a source / drain electrode 11 and 12 made of AuSn (aluminum tin). Here, the third semiconductor layer 7 is made of i-InAs
Channel layer 5 made of n-type and electron supply layer 6 made of n-GaSb
It is inserted to suppress the simultaneous generation of semi-metallic two-dimensional electrons and two-dimensional holes formed in the heterojunction system 4 with InAs and GaSb. . When the third semiconductor layer 7 is inserted, the electrostatic potential is absorbed by that layer, so that the n-GaSb valence band and the i-
It is possible to relatively vary the energy level of the conduction band of InAs. Therefore, by doping GaSb into n-type and appropriately selecting the thickness of the third semiconductor layer, an n-type ultra-high-speed HEMT 1 capable of generating only two-dimensional electrons and capable of controlling the threshold value can be realized. Furthermore, the electron supply layer is GaSb
Since it is a layer (or contains GaAs), the problem of the DX center, which has been a concern in the past, does not occur.

As described above, according to the present embodiment, the semi-metallic feature observed in the second type heterojunction system can be suppressed for the HEMT device using InAs as a channel, and the film thickness of the third semiconductor layer 7 can be reduced. The threshold can be easily controlled by the thickness. Further DX
Since an n-type HETMT device 1 without a center can be realized, it greatly contributes to the development to an ultra-high-speed device.

FIG. 4 is a view showing a second embodiment of the semiconductor device according to the present invention, wherein InAsSb and GaSbAs are used as a second kind of hetero-coupled system.
This is an example using. In FIG. 4, reference numeral 21 denotes a HEMT (semiconductor device), and the HEMT 21 is a semi-insulating substrate 22 made of GaSb.
A buffer layer 23 made of i-AlSb _0.88 As _0.12, and a second type heterojunction system 24 doped with an and-doped channel layer 25 made of i-InAs _0.95 Sb _0.05 and Te at 2 × 10 ¹⁸ cm ⁻³ . an electron supply layer 26 made of n-GaSb _0.96 As _0.04 ;
Third semiconductor layer made of i-Al _0.8 Ga _0.2 As _0.1 Sb _0.9 introduced as an intermediate layer between the channel layer 25 and the electron supply layer 26
27, a semiconductor layer 28 of i-AlSb _0.88 As _0.12 ,
Semiconductor layer (contact layer) made of GaSb _0.96 As _0.04 29
And a gate electrode 30 made of Al, and source / drain electrodes 31 and 32 made of AuTe / Au.

The semiconductor material of the electron supply layer 26 of the present embodiment is n-GaSbAs
The semiconductor material of the third semiconductor layer 27 is i (or lightly doped) -AlGaAs, and the channel layer 25 is InSbAs
It is. Therefore, even in the present embodiment, the same effect as in the first embodiment can be obtained.

〔The invention's effect〕

According to the present invention, by introducing a third semiconductor having an appropriate thickness into the heterointerface of the second type heterojunction system,
The generation of two-dimensional electrons can be generated by suppressing the generation of two-dimensional hole gas, and the threshold value can be controlled, making it easy
Electrons can be supplied to the conduction channel made of InAs-based material. As a result, due to epi configuration without DX center
InAs-based ultra-high-speed HEMT can be realized.

[Brief description of the drawings]

FIG. 1 is a view for explaining the principle of the present invention, FIGS. 2 and 3 are views showing a first embodiment of a semiconductor device according to the present invention, FIG. 2 is a sectional view showing the structure thereof, and FIG. FIG. 4 is a sectional view showing the structure of a second embodiment of the semiconductor device according to the present invention. 1, 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 containing InAs), 6, 26 channel layer (electron supply layer containing GaSb and doped with impurities) 7, 27 ... third semiconductor layer (intermediate layer containing AlSb), 8, 28 ... Semiconductor layer, 10, 30 ... Schottky gate electrode, 11-12, 31-32 ... Source / drain electrode, 2DEG ... 2D electron gas, 2DHG ... 2D hole gas.

Continued on the front page (58) Fields surveyed (Int.Cl. ⁶ , DB name) H01L 21/337-21/338 H01L 27/095 H01L 27/098 H01L 29/775-29/778 H01L 29/80-29 / 812

Claims (1)

(57) [Claims] A channel layer containing InAs; an electron supply layer containing GaSb and doped with an impurity; and an Al supply layer provided between the channel layer and the electron supply layer.
An intermediate layer containing Sb, wherein at an interface between the channel layer and the intermediate layer, generation of two-dimensional hole gas is suppressed and two-dimensional electron gas is generated. Characteristic semiconductor device.