JPS61158183A - Electrical field effect type semiconductor device - Google Patents

Abstract

PURPOSE:To lessen continuous light irradiation effect at low temperature, by a method wherein in a high electron or hole mobility transistor, donor or acceptor impurities are doped to a heterojunction surface of a super lattice layer which becomes a channel, and carriers are supplied from that donor or acceptor impurities. CONSTITUTION:An non-dope (high purity) GaAs layer 11 and GaAs layer/AlAs super lattice layers 12 are formed continuously on a semi-insulating GaAs substrate 10 by the molecular crystal growth method the same as ordinally high electron mobility transistor. This lattice layer 12 are composed of an non-dope GaAs layer 14 and an non-dope GaAs layer 15, and the doping of Si is performed to the hetero field surface of the GaAs layer 14 and AlAs layer 15 by the atomic planar doping. Furthermore, an n<+>GaAs layer 21 for contact is formed, and a source electrode 22 a drain electrode 23 are formed by alloying AuGa/Au, and a gate electrode 13 is formed with Al or Ti-Pt-Au.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention is directed to reducing carrier concentration in a carrier accumulation layer generated near a junction formed by joining two types of semiconductors with different band gaps. The present invention relates to a field-effect semiconductor device in which the impedance of a conductive path made of the electron storage layer is controlled by changing the impedance of the electron storage layer according to a voltage applied to a control electrode. In particular, the two types of bonding (
The carrier gold in the vicinity of the heterojunction is related to a high electron or hole mobility transistor supplied from a superlattice structure adjacent to the heterojunction.

[Conventional technology]

Conventionally, as an electron supply layer of a high electron mobility transistor, a method using NAiGaAak and a method using 5-G5Ag/
A method using an AILGaAa superlattice has been proposed.

FIG. 6 shows the band structure of a conventional example using the n-GaAa/AItGaAa superlattice 2. In the figure, non-
A superlattice 2 is provided adjacent to the Ga1n/ii 1 of the doped or %-Dawg, and the GaAs layer of the superlattice is doped with an impurity 1 such as S4 to form a 5-GaAa layer 5. AXG, a semiconductor with a wide gap
It is said that aAa 4 F1 is non-doped. super lattice 2
For example, the s GaAa layer 5 of zoJ and the BG of zoJ
The aAa layer and 4As layers are formed alternately, and the total layer thickness is 5001 mm. In this configuration, the superlattice conduction/
・Band 5LCB j) Donor level DL due to S-Dawg occurs at the level lowered by A7D.

A two-dimensional electron gas (2DEG) layer is formed in the Ga Am layer 1 near the heterojunction between the A10641 layer 4 and the GcbAa layer 1.
Transistor operation is possible by controlling the electron concentration n, 'fc of EG by the voltage applied to the gate metal 3.

[Problem that the invention seeks to solve]

However, in conventional devices, when N-AXGaAa is used for the electron supply layer, one of the defects peculiar to N-AJGaAa K is that the effects of light irradiation remain for several thousand hours at liquid nitrogen temperature. There is a problem (PPCper
sistent photo oosdsottvit
y), 3-Ga in Figure 6)
In the Aa/AAGαAs origin lattice, Gc of about 20λ
Since impurities are doped into a portion of the Lha layer, there is a drawback that it is difficult to control the impurity profile. For example, as shown in FIG.
It is not possible to dope only part 40' of 0, and the AJ G in the shaded area
a As 50 also has a doping profile of S (\
There are things that happen. Then, the aforementioned N AflG
A continuous light irradiation effect of aAa will occur.

Furthermore, as a conventional problem, the problem of not being able to obtain a sufficient 2DEGd degree n19 has led to various studies on ways to increase the degree of 2DEGd.

[Means for solving problems]

In the present invention, as a carrier supply layer of a high electron mobility transistor or a high hole mobility transistor,
d+pisy) k is used. APD (hereinafter referred to as interface doping) is a method in which epitaxial growth is temporarily interrupted during MflE (molecular beam crystal growth) and only impurities are deposited, and it has good controllability and easy profile control.

That is, the present invention provides a high-electron generation method using a two-dimensional electron gas or a Alternatively, in a hole mobility transistor, a superlattice is provided adjacent to the heterojunction serving as a channel, and an acceptor impurity is doped at the heterojunction interface of the superlattice, and the donor is doped from the acceptor impurity. Make sure to supply the carrier.

[Effect]

As shown in FIG. 4, according to the present invention, impurities such as Si can be doped into the hetero interface between the 0648 layer 40 and the AAGtsAa/i field. As a result, the following effects are obtained.

(2) Unlike the conventional case where N-AAGaAa is used as an electron supply layer, the electron supply layer such as the AXGaAa layer is not doped, so the RPC (memory effect of light irradiation) is reduced.

(2) The two-dimensional electron gas or two-dimensional hole gas concentration increases. The reason for this is explained below.

It is generally said that in a high electron mobility transistor (HEMT), the carrier concentration increases as the impurity level becomes shallower.

(S, lco ^I Ga S) Fig. 1 shows a band structure of an example of the present invention comprising Ga Am/%/AIGaAa Ei flat 4, and the present action will be explained using this. In the figure, a GaAs layer 11 and a G
A heterojunction is formed between the aAs/%/Ai and Aa superlattice layers 12, and a 2 DEG accumulation layer is formed near the junction.

The electron concentration of the 2DEG storage layer is controlled by the voltage applied to the gate metal 13 to operate the transistor.

The superlattice 1i112 has the AJIAa layer 14 and the GaAs layer 1
5 are formed alternately, and S( is doped) at the interface.

In the superlattice layer, there is a superlattice conduction-prone band 5LCB, and the donor level DL1 of S (decreased to a level ED lower than 5LCB) is shown as DL2. υGa S only in As layer 15
(This is the donor level when dogged. As is clear from the figure, the interface doped DL1 has a shallower level than DL2. Therefore, from the above relationship between the donor level and carrier concentration, the QDEG layer Electron density will be increased in the present invention.

The relationship between this interfacial doping and donor depth can be found in Document G.
Ba5tard Phys Etv, E24 No.
8 (Listed in 1981 P4714, No. 5
As shown in the figure, when the width of the Keiko well is plotted on the horizontal axis and the depth of the donor Ev fc is plotted on the vertical axis, the width of the quantum well is plotted on the axis, and in the case of interface doping of ■, Eo = “” + central doping of ■. In the case of EDmR, the interfacial doping of ■ is always better than the central doping of ■.
D is shallow. Note that Ro is approximately 6 mmV.

〔Example〕

FIG. 2 shows a cross-sectional main part of a HEMT according to an embodiment of the present invention, and is composed of the following parts.

Each layer is successively formed on a semi-insulating GaAa substrate 10 by the MBE method as in a normal HEMT.

11... Doped (high purity) GaAs layer, thickness 6
000λ12°”GaAs/%/Aid, 46
Superlattice layer, total layer thickness 500X, this superlattice layer 12μ, Ga As/s/AJ in Figure 1! Corresponds to Aa. Its detailed structure is as follows.

14...GaAs layer, non-doped, thickness 20λ15
...AI-Am layer, non-doped, thickness zoJ Here, the hetero interface between the GaAs layer 14 and the AgAs layer 15 is doped with p and st by the above-mentioned atomic brainer doping (APD). . For that, GaA
Growth is temporarily interrupted at the interface between a and AlAm, and G
Turn off the G beam and turn on only the A1 beam/C')i'l
, St beam is irradiated to perform only S (doping).Here, the A1 beam irradiation is continued because of the A
This is the ninth step to prevent the dissociation of #. To give a specific example, Ga
Aafi - assuming doping before growth, S equivalent to doping of I x 10"em-"
Iheem t-irradiate for 18 seconds. This j5.6X1u
Obtains a St surface density of 01%-2.For APD, see Reference J, Appl, Phya, 51(1).
, pp. 583-387 (1980, 1).

Furthermore, in FIG. 2, 21 is 1 for contact.
The 0641 layer is formed to a thickness of 300X, 22 and 245 are source and drain electrodes, which are formed by A%GJA and A%GJA, and the gate metal 13 is formed by AJL or F2T (-P t -As to form.

The increase in 2DEG concentration according to this example is shown below along with a comparative example.

Normal HEMT (N-Aft GaAa) -*
ng ~6 X 10"cm-" superlattice n-Ga
AJAJ-A HEMT with # as carrier supply layer
Moaning 〜8 X 10 etn″′
5 Examples of the present invention =ζ~? X10 a wash-5
Although the embodiments using interfacial doping with p-type impurities have been described above, it is clear that a high hole mobility transistor/distor can be formed by interfacial doping with p-type impurities.

〔Effect of the invention〕

According to the present invention, the following effects can be obtained.

■ N Aid-GaAa t- HE used as electron supply layer
34 f for μGαA# or AJilAg compared to MT.
Since there is no douging, the effect of continuous light irradiation at low temperatures is reduced.

■ Compared to RENT, which uses the s-G6 Aa/AJ Am superlattice as the electron supply layer, the doping profile of impurities such as St is more controllable (because it has the effect of gettering impurities at the hetero interface, it Compared to doping, interfacial doping has better controllability.) There are advantages.

■ Ga Am/A11. In a superlattice such as As, G
Since the level of impurities such as St in aA- is shallower at the hetero interface, there is an advantage that the concentration of two-dimensional electron gas in the channel becomes higher in the same doping pattern.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the band structure of an element according to an embodiment of the present invention;
FIG. 2 is a sectional view of a device according to an embodiment of the present invention, and FIGS. 3 and 4 show n-GaAs/AAGaAa and GaA
An explanatory diagram of the band structure of g/%/All GaAs. Figure 5 is a diagram showing the depth of the donor level of heterointerface doping and central doping. Figure 6 is a diagram of conventional 5GaAs.
/AJI A diagram showing the band structure of HH:MT using the GaAa superlattice. 10...Semi-insulating GaAa substrate 11...GaAs layer 12...(σαA8/%/Ai, Az) superlattice layer 13
... Gate metal 14 ... (superlattice) sample A1 layer 15 - (superlattice) GaAa N 21 - RGaAs layer 22 ... Source electrode 25 ... Drain electrode 1st Figure GaAs/'nz 'ALAs s case + rl
GaAs J”12 11 τ Fig. 2 Fig. 3 Fig. 4 Whistle 5 Fig. 6

Claims (1)

[Claims] 2 formed near a heterojunction between a semiconductor layer and a semiconductor layer that is lattice matched to the semiconductor layer and has a wider gap than the semiconductor layer.
In a high electron or hole mobility transistor using a dimensional electron gas or a two-dimensional hole gas, a superlattice is provided adjacent to the heterojunction serving as a channel, and a donor or acceptor impurity is provided at the heterojunction interface of the superlattice. 1. A field effect semiconductor device, characterized in that the device is doped with impurities, and a carrier is supplied from the donor or acceptor impurity.