JPS6285464A - hot electron transistor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Summary] Compound semiconductor heterojunction (GaAs-AlGaAs
) from the emitter region of GaAs.
Graded potential of aAs
The structure of the barrier layer was improved in a hot electron transistor that utilizes electrons that pass through the barrier layer and are accelerated at the interface with the base, thereby improving the characteristics.

[Industrial application field]

The present invention relates to an improvement in a hot electron transistor (abbreviated as HRT) that utilizes a telojunction of a compound semiconductor.

As research into compound semiconductors progresses, the development of semiconductor devices that take advantage of their high electron mobility is becoming more popular.

In particular, compound semiconductors using GaAs include A7! It is easy to make a ternary compound with the addition of A7! By changing the mixing ratio of , it is possible to create semiconductor layers with different characteristics, which has a wide range of applications.

In addition, MBR (Molecular Beam R
With the advancement of pitaxy technology, it has become possible to freely grow an extremely thin semiconductor layer, for example, several tens of layers, in an epitaxial layer, making it possible to use superlattice M, which Semiconductor devices, which were previously considered difficult to manufacture, are now becoming possible to manufacture.

T(ET) is one of them, and it is known that it exhibits characteristics similar to bipolar transistors by epitaxially stacking GaAs-AlGaAs in a multilayered structure, but its characteristics have not yet been put into practical use. This is insufficient and further improvement is desired.

[Conventional technology]

H using conventional graded potential barrier layer
The structures of F and T and their operating principles will be briefly explained below.

FIG. 4 shows a cross-sectional view of the structure. Semi-insulating GaAs
It has a structure in which a collector layer 2, a barrier layer 3, a base layer 4, a barrier layer 5, and an emitter layer 6 are laminated in this order on a substrate (SI-GaAs) 1.

Collector layer 2, base layer 4, and emitter layer 6 are n-type GaA
The barrier layer 3.5 is made of s-layer, and the barrier layer 3.5 is made of non-doped A llG.
It is formed by an aAs layer.

The barrier layer 5 sandwiched between the emitter layer and the base layer forms a graded potential layer.

Further, 7 indicates a base electrode, and 8 indicates an emitter electrode.

FIG. 5 schematically shows the energy level of the conduction band of the transistor having the above structure. In the barrier layer 5, the energy level shows a shape in which the energy level gradually increases linearly from the emitter layer to the base layer (graded potential).

Usually, the conduction band energy level CJ1A of AlGaAs
It changes depending on the mixing ratio of n. As the mixing ratio of Ap increases, its potential level tit: -IT, W increases.

Therefore, in order to form a graded potential as shown in FIG. 5, layers are stacked each time the growth is performed while controlling the evaporation of the source A1 by the M[R method.

The mixing ratio X is im usual A e x G a 1- x A
While forming the above barrier layer,
This is obtained by sequentially changing the X value such that it is 0.3 at the interface with the base layer and becomes 0 at the interface with the emitter layer.

When a negative voltage is applied to the emitter and a positive voltage to the collector with reference to the base to each of the emitter, base, and negative electrodes of the above structure, the energy level diagram in FIG. 5 changes as shown in FIG. 6.

The energy level of the barrier layer 5 is changed from an upward slope to the right by the bias potential between the emitter and the base, and becomes n''.
- The conduction band electrons of the emitter layer made of GaAs overcome the barrier layer, are accelerated by the amount of AEC at the hetero interface with the base layer, become hot electrons, and are injected into the base region.

Furthermore, it passes through the base region at high speed and A on the collector side
The barrier layer 3 made of 11 Ga As is reached.

Since the barrier layer on the collector side has an X value of 0.2, it easily crosses the barrier and reaches the collector region.

This electron operation is very similar to that of a bipolar transistor, and its switching characteristics are extremely fast, so it is called a HET and is expected to be used as a high-speed, high-frequency device.

[Problem that the invention seeks to solve]

The HET tank structure using the graded potential barrier layer described above requires accurate control and change of the mixing ratio of A1 within the barrier layer, which is not good for controlling sex organs.

Furthermore, even if a barrier layer can be formed using the MBR method,
7! The thickness of the barrier layer becomes large to control the
The thickness is usually 300 Å or more. Therefore, there is a problem that a large current density necessary for high-speed operation cannot be obtained.

Another problem is that in the case of a structure in which the barrier layer is doped to supply two-dimensional electron gas to the base layer, an undesirable memory effect due to light irradiation occurs.

[Means for solving problems]

The above problem arises in a HET structure that uses a graded potential layer as a barrier layer between the emitter and base, and the structure of the graded potential barrier layer is as follows:
This is solved by the structure of the present invention, which consists of forming graded potentials using quantized potentials from multiple heterojunctions of AlGaAs and GaAs.

[Effect]

The multiple heterojunction of AρG a A s and GaAs is G
When the thickness of the aAs layer is thin, a quantum well is formed, and the ground level of the potential in the quantum well has a characteristic that the narrower the width of the well, the higher the potential level.

In the present invention, a step-like potential barrier is formed by selecting the width of the quantum well to be, for example, 40 and 10. This makes it possible to construct a thinner barrier than the conventional structure, and obtains a large current density. It has become easier.

〔Example〕

An embodiment according to the present invention will be explained in detail with reference to FIG. Explanation of the same reference numerals as those used in the prior art section will be omitted.

The barrier layer 5, which will be explained in the prior art section, is constructed from multiple heterojunctions in FIG.

That is, A I2 G a A 8 layers9. In, 11
The three layers are laminated in a sand-like manner with non-doped GaAs layers 12 and 13 sandwiched therebetween.

The energy level diagram of the barrier layer at this time is shown in FIG. and 40 people.

The GaAs layers 12 and 13 form a superlattice nested well, and the energy basis Y11 layer in this quantum well is shown by the dashed line in FIG. It is clear from the figure that the base units have different heights in layers 12 and 13 due to the difference in the width of the wells.

In other words, the units in each quantum well are made to become higher sequentially from the emitter to the base, and the barrier layer is substantially similar to the conventional graded potential, as shown in Figure 2 (11). Works with equivalent functionality.

The total thickness of the potential barrier layer in the above structure is 110
The thickness of the conventional graded potential layer is 3.
This is significantly smaller than the average of 00 people. As a result, the current density from the emitter layer can be significantly improved compared to the conventional structure.

Another embodiment of the barrier layer will be described with reference to FIG. The difference from Fig. 2 fa+ is that the Ga As layer 1
2, a planar doping layer 14 is provided, and non-doped GaAs is used for the base layer.

Planar doping temporarily suspends the growth of the GaAs layer,
This is done by irradiating the surface with Si, and the sheet concentration is chosen to be 6 XIO"cm-".

The planar doping layer 14 is made of Al! A two-dimensional electron gas is supplied at the interface between the GaAs layer 9 and the non-doped GaAs base layer 4, and is used as a carrier for the base layer. This results in a base layer sheet resistance of 50 to 10
A low resistance of 0Ω/cm2 can be obtained.

〔Effect of the invention〕

As explained above, by using multiple heterojunctions of AβGaAs and GaAs for the barrier layer between the emitter and the base, it is possible to form a graded potential barrier layer that is significantly thinner than conventional ones, allowing a high current density. II ET can be produced.

[Brief explanation of drawings]

FIG. 1 is a structural cross-sectional view of I (I: i, T) according to the present invention, FIG.
゛Energy unit diagram of a potential barrier. Figure 3 is an energy level diagram for explaining another embodiment of the present invention. Figure 4 is a cross-sectional view of a conventional HET structure. Figure 5 is a conventional structure. FIG. 6 shows the energy unit diagram of IIP:T during its operation. In the drawings, 1 is a semi-insulating GaAs substrate, 2 is a collector layer, 3 is a barrier layer, 4 is a base layer, 5 is a graded potential barrier layer, 6 is an emitter layer, 7 is a base electrode, and 8 is a base electrode. 9.10.11 is an A12GaAs layer, 12 and 13 are undoped GaAs layers, and 14 is a planar doped layer. Patent applicant: Director of the Agency of Industrial Science and Technology Tatsu Todoroki Figure 2 F-FI Oc'+cn ++rCO,
−−，−− Third! ! I GaAS) Sub @ 5 HET Yo 1 Drunken Figure 4 Figure 5 tjJ4'? Figure 6 of Fight-T Half Rookie ￥fL

Claims (1)

[Claims] Collector layer (2) made of compound semiconductor on substrate (1)
, a hot electron transistor structure in which a barrier layer (3), a base layer (4), a graded potential barrier layer (5), and an emitter layer (6) are sequentially laminated, the structure of the graded potential barrier layer (5). A hot electron transistor characterized in that it is formed by multiple heterojunctions and uses a multiple quantum potential that increases sequentially from the emitter to the base.