JPH03104126A - Compound semiconductor device - Google Patents

Abstract

PURPOSE:To make it difficult for electrodes to flow in a gate electrode from an electron feeding layer and to improve breakdown strength of the gate by a method wherein a high-resistance layer having an electron affinity smaller than that of the electron feeding layer is provided between the gate electrode and the electron feeding layer. CONSTITUTION:A buffer layer 2, a first compound semiconductor layer 3, a second compound semiconductor layer 4 and a third compound semiconductor layer 5 are laminated on a compound semiconductor substrate 1. The electron affinity of the layer 4 which is an electron feeding layer is smaller than that of the layer 3, which is an electron travelling layer, and the electron affinity of the layer 5 which is a high-resistance layer is smaller than that of the layer 4. A resist pattern for forming a gate electrode 6 is formed on the layer 5 to deposit an Al film and the electrode 6 is formed. Then, the layer 5 is removed using the electrode 6 as a mask, source and drain electrodes (source and drain layers) 7 and 8 are formed on the layer 4 on both sides of the electrode 6 and an impurity is made to diffuse up to the interior of the layer 3 by a diffusion heat treatment to form alloy layers. Electrons are fed from the layer 4 to the layer 3 and a two-dimensional electron gas layer is formed. Thereby, a source-drain resistance is made low and a gate breakdown strength can be made high.

Description

[Detailed Description of the Invention] [Summary] Regarding a compound semiconductor device, with the aim of a compound semiconductor device having high breakdown voltage and high electron mobility in the microwave band, first compound semiconductor layers sequentially stacked on a compound semiconductor substrate, Second compound semiconductor layer. a third compound semiconductor layer;
a gate electrode in contact with the third compound semiconductor layer; source/drain electrodes arranged on both sides of the gate electrode and electrically connected to the second compound semiconductor layer; The semiconductor layer includes an electron transport layer having a lth electron affinity, the second compound semiconductor layer having an electron supply layer having a second electron affinity smaller than the first electron affinity, and the third compound semiconductor layer having an electron transport layer having a second electron affinity.
The compound semiconductor layer is constituted by a compound semiconductor device which is a high resistance layer having a smaller electron affinity than the second compound semiconductor layer.

[Industrial application field]

The present invention relates to a compound semiconductor device.

There is a demand for compound semiconductor devices having high breakdown voltage and high electron mobility in the microwave band.

Currently, microwaves are used for communication with remote islands and depopulated areas, and for satellite broadcasting. In order to amplify high-power microsignals, an amplification element that can withstand the signals is required.

[Conventional technology]

Conventional. High electron mobility transistor (HEMT) is a compound semiconductor device that has electron mobility in the microwave band.
).

FIG. 4 is a cross-sectional view for explaining a conventional high electron mobility transistor, in which 1 is a compound semiconductor substrate, 2 is a buffer layer, 3 is an electron transport layer, 4 is an electron supply layer, 6 is a gate electrode, and 7 is a cross-sectional view for explaining a conventional high electron mobility transistor. , 8 are source/drain electrodes, and 2DEC is a two-dimensional electron gas.

By the way, since the electron supply layer 4 has a high impurity concentration and a low potential barrier with the metal layer of the gate electrode 6, when a large signal is applied to the gate, a large gate current flows, causing the problem that the amplification operation becomes impossible. arise. Additionally, as a result of a large amount of gate current flowing, there is the problem that functionality deteriorates and the reliability of the transistor decreases.

If the impurity concentration of the electron supply layer 4 is lowered and the resistance is increased, the gate breakdown voltage will increase, but this will cause a problem such as an increase in source/drain resistance.

(Problems to be Solved by the Invention) Therefore, problems arise in conventional high electron mobility transistors when amplifying a large signal microwave input.

The present invention is. Due to the structure that increases the gate breakdown voltage, the source
An object of the present invention is to provide a compound semiconductor device that can reliably amplify a large microwave input signal without increasing drain resistance.

[Means to solve the problem]

FIG. 1 is a cross-sectional view for explaining the compound semiconductor device of the present invention, in which 1 is a compound semiconductor substrate, 2 is a buffer layer,
3 is a first compound semiconductor layer, which is an electron transport layer; 4 is a second compound semiconductor layer, which is an electron supply layer; 5 is a third compound semiconductor layer, which is a high resistance layer; 6 is a gate electrode; 7,
8 represents a source/drain electrode, and 2DEG represents a two-dimensional electron gas.

The above problem is solved by the first compound semiconductor layer 3, the second compound semiconductor layer 4, and the third compound semiconductor layer stacked sequentially on the compound semiconductor substrate l.
a compound semiconductor layer 5, a gate electrode 6 in contact with the third compound semiconductor layer 5, and source/drain electrodes arranged on both sides of the gate electrode 6 and electrically connected to the second compound semiconductor layer 4. 7 and 8, the first compound semiconductor layer 3 is an electron transit layer having a first electron affinity, and the second compound semiconductor layer 4 is an electron transit layer having a second electron affinity smaller than the first electron affinity. This problem is solved by a compound semiconductor device in which the third compound semiconductor layer 5 is a high-resistance layer having a smaller electron affinity than the second compound semiconductor layer 4.

[Effect]

In the present invention, as shown in FIG.
In between, a high resistance layer 5 having a lower electron affinity than the electron supply layer 4 is formed.
is provided. Figure 2 is its energy band diagram. By providing the high resistance layer 5, the potential barrier becomes high, making it difficult for electrons to flow from the electron supply layer 4 to the gate electrode 6. As a result, even if a large microwave signal is manually applied to the gate, the gate current will hardly flow, improving the gate withstand voltage.

On the other hand, the electron supply layer 4 connected to the source/drain electrodes 7 and 8 can maintain low source/drain resistance.

(Example) Figure 3(a). (b) is a cross-sectional view for explaining an example, where l is a compound semiconductor substrate, 2 is a buffer layer. 3
is the l-th compound semiconductor layer, which is the electron transit layer, and 4 is the second compound semiconductor layer.
The compound semiconductor layer is an electron supply layer. 5 is a third compound semiconductor layer, which is a high resistance layer; 6 is a gate electrode; 7.8
The source/drain electrode 32DEC represents a two-dimensional electron gas.

Hereinafter, steps for manufacturing the compound semiconductor device of the present invention will be explained with reference to these figures.

FIG. 3(a) A buffer layer is formed on the reference compound semiconductor substrate l. The first compound semiconductor layer 3, the second compound semiconductor layer 4, and the third compound semiconductor layer 5 are laminated by molecular beam epitaxy (MBE).

The composition and thickness of each layer are as follows.

1. Compound semiconductor substrate GaAs 2. Buffer layer GaAs 2000 people 3. First compound semiconductor layer GaAs 300 people 4.
Second compound semiconductor layer (n-doped) n”-AIGaAs 600
People 5. Third compound semiconductor layer (undoped) i -AIGaAs 150 people See Figure 3(b) On the third compound semiconductor layer 5, a resist pattern (not shown) for gate electrode 6 is formed. Aluminum (At) is then vapor-deposited to form the gate electrode 6.

Using the gate electrode 6 as a mask, the third compound semiconductor layer 5 is
Remove by etching.

Next. Second compound semiconductor layer 4 on both sides of gate electrode 6
AuGe/Ni/Au is deposited thereon to form source/drain electrodes 7.8, and diffused into at least the first compound semiconductor layer 3 by diffusion heat treatment to form an alloy layer.

Electrons are supplied to the electron transport layer 3, which is the first compound semiconductor layer, from the electron supply layer 4, which is the second compound semiconductor layer, and a two-dimensional electron gas is formed.

In this way, a compound semiconductor device with low source/drain resistance and high gate breakdown voltage is realized.

This compound semiconductor device. Large signal input in the microwave band. Amplify reliably.

Note that the second compound semiconductor layer 4, which is an electron supply layer, has a lower electron affinity than the first compound semiconductor layer 3, which is an electron transit layer, and the third compound semiconductor layer 5, which is a high resistance layer, has a lower electron affinity than the first compound semiconductor layer 3, which is an electron transit layer. The electron affinity is smaller than that of the compound semiconductor layer 4. In the embodiment, i-AIGaAs is used as the third compound semiconductor layer 5.
However, AIAs and AI, which have even smaller electron affinities,
A compound semiconductor layer such as Sn can also be used.

〔Effect of the invention〕

As described above, according to the present invention, a compound semiconductor device with low source/drain resistance and high gate breakdown voltage can be realized.

The compound semiconductor device of the present invention is highly effective in amplifying adult power signals in the microwave band.

It is.

In the figure, 1 is a compound semiconductor substrate, 2 is a buffer layer, 3 is a first compound semiconductor layer, which is an electron transport layer, 4 is a second compound semiconductor layer, which is an electron supply layer, and 5 is a third compound semiconductor layer. The semiconductor layer is a high resistance layer, and 6 is a gate electrode. 7.8 is the source/drain electrode. 2DEG is two-dimensional electron gas

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view for explaining the compound semiconductor device of the present invention, Fig. 2 is an energy band diagram, and Fig. 3(a). (b) is a sectional view for explaining the embodiment, and Figure 4 is a sectional view of the conventional example.

Claims (1)

[Claims] A first compound semiconductor layer (3), a second compound semiconductor layer (4), and a third compound semiconductor layer, which are sequentially stacked on a compound semiconductor substrate (1).
a compound semiconductor layer (5), and a third compound semiconductor layer (5);
a gate electrode (6) in contact with the gate electrode (6);
), the first compound semiconductor layer (3) has source/drain electrodes (7, 8) arranged on both sides of the second compound semiconductor layer (4) and electrically connected to the second compound semiconductor layer (4); the second compound semiconductor layer (4) has an electron affinity of
The third compound semiconductor layer (5) is a high-resistance layer that has a smaller electron affinity than the second compound semiconductor layer (4). Characteristic compound semiconductor device.