JPS60196976A - Semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a stable film, and to prevent the flowing of gate-leakage currents through a gate electrode by isolating an impurity doping layer and a layer, in which electrons are made to travel, and using a metal-oxide-semiconductor junction as the gate electrode in the layer, in which electrons are made to travel. CONSTITUTION:A high purity GaAs layer 2 and an N type GaAlAs layer 3 are formed on a semi-insulating GaAs substrate 1, an oxide 9 is shaped on the GaAl As layer 3, and a source 6 and a drain 8 as ohmic electrodes and a metal as a gate electrode 7 are formed, thus constituting a transistor. The N type GaAlAs layer 3 is an impurity doping layer as an electron donor, stores carriers on the interface between the layer 3 and the high purity GaAs layer 2, and modulates drain currents through the gate electrode 7. A stable film is obtained by oxidizing GaAlAs, extremely small gate-leakage currents flow through the gate electrode, and logic amplitude is taken in a large value.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Application of the Invention The present invention relates to a field effect transistor with extremely excellent high-speed switching characteristics. A circuit element in which this transistor is integrated is suitable for use as a logic element for an ultra-high-speed computer, for example.

[Background of the invention]

A new field effect transistor has been developed in which electrons generated on the Q a As side are controlled by a gate electric field by bringing non-doped Ga As and n-type AfiGaAs into contact (Nikkei Electronics 1980.7.
21 P, 66-69). AQGaAs donor impurity
Since electrons from donors are collected on the Ga As side, electrons can travel at low temperatures without being scattered by impurities.
Mobility can be increased.

However, since this 1-transistor uses a Schottky gate, it has been found that a gate leak current flows through the gate electrode, making it impossible to obtain a large logic amplitude.

[Purpose of the invention]

An object of the present invention is to provide a semiconductor device, which is a new field effect transistor, which has a structure in which a stable film is obtained and no gate leakage current flows through the gate electrode.

[Summary of the invention]

The present invention uses a selective doping method to separate an impurity doped layer that serves as an electron donor and a layer through which electrons run, and also forms a metal-oxide-semiconductor junction (referred to as MO8 junction) in the layer through which electrons run. It is used as a gate electrode.

FIG. 1 shows the basic structure of the present invention. A cross-sectional view of the element is shown. Semi-insulating GaAs substrate (specific resistance: 10°Ω・c
m) High purity QaAsJ12 and n-type GaAQAs layer 3 are provided on 1.

Further, an oxide 9 is formed on the GaAΩAs layer 3, and a source 6, a drain 8, which serves as ohmic electrodes are formed. A transistor is constructed by providing a metal as a gate electrode 7. n type c
The aAnAs layer 3 is an impurity-doped layer that serves as an electron donor, and stores carriers at the interface between the GaAQAs layer 3 and the high-purity GaAs layer 2, and transfers these carriers to the gate electrode 7.
modulates the drain current through the

[Embodiments of the invention] Examples will be described below.

Example 1 High-purity n-type GaAs 2 was deposited on a semi-insulating GaAs substrate 1 by a well-known liquid phase growth method, and then n
+-type GaAQxAsx-x (x=0.4)3 was grown to 0.3 μm and 0.1 μm, respectively. n-type GaAs2
is undoped, n+ type GaAnAs3 is doped with Sn, and has a carrier concentration of 5 x 1017 cm-3. After that, the 5i02 film was made into 3 layers using SiH4 gas thermal decomposition method.
Covers 500 people. On top of this, patterns that will become source and drain electrodes are formed by processing using normal photoresist. Next, etching was performed until the n-type GaAQ layer 2 was reached. After etching.

AuGeNd-based Kinku 5 was used as a metal target and an ohmic electrode. After forming the source and drain electrodes, the n-type GaARAs was oxidized in oxygen plasma to form an oxide film 9 with a thickness of 1000 nm. After forming the oxide film, A u as the gate metal 7
/ M o. That is, Mo(
Molybdenum) metal and gold (Au) were continuously deposited on the Mo metal. Next, a photoresist film is left as a gate pattern by processing using a photoresist. Using this photoresist film as a mask, A'u is ion-etched, and M
A gate electrode was formed by plasma etching O with CF4 (Freon) gas. As a result, a film made of oxidized GaAQAs has better heat resistance than a film made of oxidized GaAs, and has a flat band voltage of V□, ·. was achieved with good reproducibility. Originally, the electron mobility in GaAQAs3 is small, but this device uses undoped Ga as a channel.
Since A s is used, electrons can be moved with high electron mobility. Therefore, it is a great advantage to be able to stably produce an oxide film. Also, operate in depression type, source, goo 1~. The structure separates the drains, reducing input capacitance and allowing high-speed operation.

Example 2 Among the manufacturing methods shown in Example 1, undoped GaAs2.
n-type GaAl2As3 was formed by molecular beam epitaxial method. Molecular beam epitaxial method is 10”-9 Tor
Ga, As in an ultra-high vacuum below r.

From each oven of AQ, Ga and As for 2, Ga' for GaAQAs, and 3.
, AQ.

GaAs and GaAQAs were formed on a semi-insulating GaAs substrate by simultaneously converting As and Si, which serves as an impurity source, into molecules. The rest is the same as in Example 1.

〔Effect of the invention〕

The features of the present invention can be summarized as follows.

A transistor using two-dimensional conduction phenomenon using a heterojunction (GaAQAs/GaAs)
As oxide film/GaA (lAs/GaAs layered structure is formed. GaAQAs is directly oxidized.

The effects are as follows.

(1) A stable film can be obtained by oxidizing GaAQAs.

(2) Gate leakage current flowing through the gate electrode is extremely small, so the logic amplitude is large.

(3) Since the gate oxide film capacitance and the depletion layer capacitance are connected in series, the input capacitance of the device can be reduced, and therefore high-speed operation can be achieved.

(4) A GaAQAs-based oxide film has a high dielectric constant and has little voltage loss at the gate applied voltage.

Naturally, undoped GaAs2 and semi-insulating Ga
Even if p-type GaAs or p-type GaAQAs is inserted between the As substrate 1, there is no difference in operation and the present invention is applicable.

The present invention can be applied to high-speed logic ICLSI, low-noise amplification elements in the microwave band, and high-output elements.

In addition, as another material, undoped r n
1-X A Q X A s, type II In1y
It is also possible to oxidize the n-type I 111-y A Q y As after forming AQyAs.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a semiconductor device of the present invention. ■...Semi-insulating GaAs substrate, 2...Undoped or high purity GaAs, 3-n0 type GaAQA
s. 4-n-type GaAs, 5-AuGe-Ni metal, 6.8... Wiring metal for source and drain electrodes. 7...Goo 1~Kanai, 9...GaAQAs oxide film. Straw 1 diagram

Claims (1)

[Claims] A first semiconductor layer that does not substantially contain impurities and a second semiconductor layer that contains impurities are formed on a predetermined semiconductor substrate so that electrons are formed near the interface between the first and second semiconductor layers. The first and second semiconductor layers of the first semiconductor layer are laminated so as to be stored, and an electrode for controlling electrons is sandwiched between the second semiconductor layer and the second semiconductor layer with the missing object layer interposed therebetween. The first point is electrically connected to the electrons stored near the interface of the semiconductor layer. A semiconductor device comprising at least a second electrode.