JPH02206170A - Hot electron transistor - Google Patents

Abstract

PURPOSE:To obtain IC-VBE characteristics not presenting negative resistance by providing a resonance tunnel having a well with a specified thickness while forming the interface so as to have a low degree of flatness on the level of atomic layer. CONSTITUTION:An emitter barrier layer 6 is formed between a base layer 5a and an emitter layer 7, and a resonance tunnel is provided in the emitter barrier layer 6. The resonance tunnel has a well with a thickness of 20-35Angstrom . During growth of the well, temperature of a semi-insulative substrate 1 is held low at about 400 deg.C so that flatness of the interface on the level of atomic layer becomes of a low degree. If the well is narrower than 20Angstrom , it will not function as a quantum well. If it is wider than 35Angstrom , negative resistance will be presented. According to this arrangement, IC-VBE characteristics not presenting negative resistance can be obtained while a resonance tunnel structure is used, namely, while a current density is kept high.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a hot electron transistor (Hot
We aim to improve the current density of electron transistor (hereinafter referred to as HET).
”Regarding.

<Conventional technology> FIG. 1 shows a configuration diagram of a conventional HBT.

In the figure, 1 is a semi-insulating InP substrate, and 2a.

2b and 2c are contact layers made of n+-InGaAs, 3a is a collector layer, and 3b is a collector electrode.

4 is a collector barrier layer made of InAlAs, and 5a is n
- a base layer made of 1nGaAs; 5b is a base electrode;
6 is an emitter barrier layer made of TnA/As, and 7 is an n-
The emitter layer 28 made of InGaAs is an emitter electrode. Note that the collector barrier layer between the collector base is 1
About 5008.

The emitter barrier layer between the base and the emitter is about 1,508 mm thick, and the base layer is about 1,000 mm thick using, for example, a molecular beam crystal growth apparatus (MBE).

FIG. 3 shows an energy band configuration diagram of the above-mentioned HET. In the figure, both the base and emitter layers are GaA.
However, an extremely thin InAlAs layer of about 150 Å is inserted between these layers as a barrier layer. For this reason,
Electrons entering the base region from the emitter are formed by InGa
The energy is incident with an energy difference of 0.6 eV or more between As and InAl As. This indicates that electrons are traveling at extremely high speeds, passing through the base layer with a thickness of about 100 OA in less than O,lps.1This means that the electrons operate at extremely high speeds compared to normal bipolar transistors. is possible.

FIG. 4 shows the ICVBE characteristics of such a HET.

However, since the current density of the tunnel current is not very large (<10'A/cm2 or less), high-speed operation is difficult when it is made into a device.

In order to solve this problem, quantum wells (for example, InGaAsAl) are formed in the emitter barrier layer as shown in FIG.
In the case of As-based, the total thickness of the emitter barrier layer is 100 to 1
If the thickness of the quantum well is about 108, the thickness of the quantum well is about 40 to 508. In the case of GaAs-AlAs, if the thickness of the entire emitter barrier layer is about 90 to 1308, the thickness of the quantum well is about 5.
By forming the emitter barrier into a resonant tunnel barrier (with a thickness of approximately 0 to 80 mm), the transmission probability is improved and the current density can be increased to approximately 105 A/cm2 (resonant tunnel type) (ET ( (hereinafter referred to as RHET) is known.The temperature of the GaAs substrate 1 when forming the quantum well is heated to approximately 550 to 700°C, and temperature control of the substrate is important for improving the flatness of the interface. It becomes an element.

<Problems to be solved by the invention> However, as shown in Figure 6, RHET
The characteristics now show negative resistance, making it a logic integrated IC that is suitable for boat fishing.
The problem was that it was difficult to form.

The present invention has been made to solve the problems of the prior art described above, and aims to realize a HET that has a current density comparable to that of a RHET and has improved Ic-VBE characteristics.

Means for Solving the Problems> In order to solve the problems of the prior art described above, the present invention has a structure in which a collector barrier layer is provided between the collector layer and the base layer, and an emitter barrier layer is provided between the base layer and the emitter layer. HET having a resonant tunnel formed in the emitter barrier layer, characterized in that the well width of the resonant tunnel is set to a thickness of 20 to 35 A, and the interface is formed with rough flatness at the atomic layer level. It is.

<Example> The present invention will be described below with reference to nine drawings. FIG. 1 shows the configuration of an embodiment of the HET of the present invention, and the drawing is similar to the conventional example.

In the present invention, the width of the well formed in the emitter barrier layer 6 is 20 mm.
The temperature of the semi-insulating substrate 1 during growth of the well is maintained at about 400°C.

In this way, by lowering the growth temperature to a lower temperature than before, the flatness of the interface at the atomic layer level can be made rougher.

Note that if the quantum well is narrower than 208 µm, it no longer functions as a quantum well, and if it is wider than 35 µm, a negative resistance characteristic appears.

As mentioned above, by narrowing the well width, the first resonance level increases and the P/V ratio (peak/valley ratio...5
The ratio of the A part to the mouth part shown in the figure) becomes smaller (the current value in the valley increases). Furthermore, if the flatness of the interface is rough, "shaking" occurs in the resonance level, resulting in a decrease in the P/■ ratio.

The material of the HBT may be InGaAs-Aj7As or GaAs-AlGaAs.

FIG. 2 shows the IcVBE characteristics of the HET manufactured using the present invention, and FIG. 1 shows that the negative resistance characteristics are improved.

<Effects of the Invention> As specifically explained above in conjunction with the embodiments, according to the present invention, the well width of the resonant tunnel can be set to a thickness of 20 to 35 mm, and the flatness of the interface at the atomic layer level can be made rough. Therefore, although it has a resonant tunneling structure (that is, the current density remains high), its J-V characteristic does not exhibit negative resistance.

Therefore, HE is fast, easy to design, and has good controllability.
It is possible to achieve T. .

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of the present invention and a conventional NET. Figure 2 shows the HET Ic-■ manufactured using the present invention.
BE characteristic diagram, Figure 3 is the energy band configuration diagram of the conventional HE 'I', Figure 4 is the 1cvBE of the conventional HE 'T'
FIG. 5 is an energy band configuration diagram of a conventional RHET, and FIG. 6 is an IcVBE characteristic diagram of a conventional RHET. 1... Semi-insulating GaAs substrate, 2a, 2b, 2C...
- Contact layer, 3a... Collector layer, 3b... Collector electrode, 4... Collector barrier layer, 5a,...
Base layer, 6... Emitter barrier layer, 7... Emitter layer.

Claims (1)

[Claims] A collector barrier layer is formed between the collector layer and the base layer, an emitter barrier layer is formed between the base layer and the emitter layer,
In the hot electron transistor having a resonant tunnel in the emitter barrier layer, the well width of the resonant tunnel is set to a thickness of 20 to 35 Å, and the flatness of the interface at the atomic layer level is made rough. transistor.