JPH02128480A - Tunnel diode type semiconductor device - Google Patents

Abstract

PURPOSE:To make a valley current small to increase the ratio of it to a peak current of a diode so as to improve a semiconductor element of this design in performance by a method wherein layers other than a quantum well layer constituting a tunnel diode are formed of a semiconductor layer whose valence band width is large. CONSTITUTION:The following are provided onto an N-type InAs substrate 6 to constitute a diode: an N-type InAs layer 7; an undoped GaAs layer 1 of 7nm thickness, an undoped AlNb layer 2 of 3nm thickness; an undoped InAs layers 3 of 7nm thickness; an undoped AlNb layer 4 of 3nm thickness; and an undoped GaAs layer 5 of 50nm thickness. And an n-type InAs layer 8 is epitaxially grown thereon, an electrode 10 of AuGeNi alloy is fitted to the layer 8, and an electrode 9 like the electrode 10 is fitted to the rear side of the substrate 6. The diode is composed as mentioned above, and when a voltage is applied to the electrode 9 as an anode and the electrode 8 as a cathode, a quantum level in each InAs layer is located lower than the valence band of the layers 5 and 3, so that a tunnel current penetrates the layers 5 and 4 and flows to the layer 1 penetrating the layer 2 via the quantum level of the layer 3. If the voltage is made to increase furthermore, electrons are blocked by the layer 1 and consequently a current does not flow.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a tunnel diode type semiconductor device, and in particular is formed of semiconductor layers having different electron affinities or different sums of electron affinities and forbidden band widths. This invention relates to a tunnel diode type semiconductor device using quantum levels.

[Conventional technology]

Tunnel diodes, which use quantum levels formed by semiconductor layers with different electron affinities or semiconductor layers with different electron affinities and forbidden band widths, have attracted increasing attention in recent years because of their ability to obtain large negative resistance, especially at low temperatures. It is something that exists. This type of tunnel diode transmits a quantum layer formed by, for example, a gallium arsenide (hereinafter referred to as GaAs) layer and a semiconductor layer having a lower electron affinity than this layer, such as an aluminum gallium arsenide (hereinafter referred to as A, RGaAs) layer. It operates by controlling electrons with electrode voltage.

Now, in such a semiconductor device, for example, electrons are
A 4 G a As layer and barrier
However, it is a tunnel current in the A,ffGaAs layer, and generally speaking, the higher the aluminum composition, that is, the greater the amount of discontinuity in the valence band between the GaAs layer and the A I Ga As layer, the more the AρGaAs The thicker the layer, the lower the chance of penetration. Therefore, in order to increase the amount of current that passes through it, it is necessary to make the ApGaAs layer thinner to a certain extent, but in order to form a quantum level, it must be thinner than a certain level.

Therefore, the thickness of A(lGaAs) is about 5 nm.

[Problem to be solved by the invention]

Electrons passing through the A Il Ga As layer in this way are a tunnel phenomenon, and determine the peak current of the peak current and valley current seen in the current-voltage characteristics of the diode. On the other hand, the valley current depends on electrons exceeding the energy barrier made of AρGaAs, so in order to reduce the valley current, it is possible to use a large barrier of A, &As or to increase the depth of the quantum well by using strained InGaAs. is being attempted.

However, by increasing such an energy barrier, the probability of electron tunneling decreases, and the peak current decreases. Therefore, the ratio of peak and valley currents does not show much improvement.

An object of the present invention is to provide a tunnel diode type semiconductor device with a large peak to valley current ratio.

[Means to solve the problem]

In the tunnel diode type semiconductor device of the present invention, a second semiconductor layer having an electron affinity larger than the sum of the electron affinity and the forbidden band width of the first semiconductor layer is provided on the first semiconductor layer; A third semiconductor layer having an electron affinity larger than that of the first semiconductor layer is provided on the semiconductor layer, and a third semiconductor layer having an electron affinity smaller than that of the third semiconductor layer is provided above the third semiconductor layer. A fourth semiconductor layer is provided, and a fifth semiconductor layer is provided on the fourth semiconductor layer, the sum of the electron affinity and the forbidden band width being smaller than the electron affinity of the third semiconductor layer. It is characterized by forming a quantum well.

[Effect]

The electron affinity of indium arsenide (hereinafter referred to as InAs) is greater than the sum of the affinity of gallium antimonide (hereinafter referred to as GaSb) and the forbidden band.
A quantum well structure is formed by providing a layer, but when GaSb is further placed on both ends of the layer, holes in GaSb pass through AρGaSb, pass through the quantum level in the InAs layer, and return to AβGaSb. passes through, and current flows.

Therefore, in GaSb, since there is a forbidden band of GaSb, the hole dependence position is below the valence band of GaSb.

In conventional tunneling diodes, electrons are dependent on the outside of the quantum well and therefore pass through the barrier, resulting in a valley current.

However, in the present invention, the transmitted charge electrons are holes and do not cross the barrier because they depend on the energy level below the valence band. Therefore, the valley current can be kept low.

〔Example〕

First, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view of the main parts of an embodiment of the present invention.

In this example, an n-type InAs substrate 6 is coated with an n-type InAs substrate 6.
An s layer 7 is provided, a non-doped GaSb layer 1 with a thickness of 7 nm as a first semiconductor layer, and a thickness of 3r+ as a second semiconductor layer.
An n+ non-doped GaSb layer 2, a 7 nm thick non-doped InAs layer 3 as a third semiconductor layer. Non-doped A with a thickness of 3 nm as the fourth semiconductor layer! O3b layer 4, 5th
A non-doped GaSb layer 5 with a thickness of 50 nm is provided as a semiconductor layer, and an n-type InAs layer 8 is further epitaxially grown. The electrodes 9 and 10 are made of evaporated gold-germanium-nickel alloy.

FIG. 2 is an energy band state diagram in a thermal equilibrium state in the depth direction under the electrode 10 in the tunnel diode of this embodiment.

Here, the second. Third. A quantum well structure is formed by the fourth semiconductor layer, and a quantum level is formed in the third semiconductor layer.

Next, a voltage is applied with electrode 9 being positive and electrode 10 being negative. FIG. 3(a) is an energy band state diagram at this time. By applying a voltage, the quantum level in InAs is located below the valence band edge of the GaSb layer 5,
a S b Located below the valence band edge of layer 1.

Therefore, in this state, the tunnel current passes through the Apsb layer 4 through the GaSb layer 5, passes through the quantum level of the InSb layer 3, passes through the Apsb layer 2, and flows to the GaSb layer 1.

Furthermore, an energy band phase diagram when the applied voltage is increased is shown in FIG. 3(b). At this time, InAs
The quantum level therein is lower than the valence band edge of the GaSb layer 5 but located above the valence band edge of the GaSb layer 1. Therefore, electrons that have passed through the AfflSb layer from the GaSb layer are blocked by the GaSb layer 1 and do not flow.

On the other hand, the conventional structure, that is, the first and fifth semiconductor layers (G
In the structure without the aSb layer 1.5), the holes injected from the InAs 7 have an energy distribution, so even if the quantum level and the valence band edge in the InAs layer 6.7 do not match, the current will be small. flows to Furthermore, since the AfflSb layer 2.4 is thin, the number of electrons that cross the energy barrier increases, resulting in a poor peak current to valley current ratio.

In the above embodiment, Apsb layers were used as the second and fourth semiconductor layers, but the present invention can be similarly applied even if mixed crystals of Apsb and GaSb are used as long as the thickness is sufficient to conduct tunneling current. .

〔Effect of the invention〕

As is clear from the above description, the present invention has the advantage that it is possible to reduce the valley current by using a layer with a large valence band edge as a layer outside the quantum well layer. The present invention has the effect that the ratio between the peak current and the valley current of a type semiconductor device can be increased, and the performance of the semiconductor element can be improved compared to the conventional one.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the main parts of an embodiment of the present invention, and FIG.
The figure is an energy band state diagram of the embodiment shown in FIG. 1 in a thermal equilibrium state, and FIGS. 3(a) and 3(b) are energy band state diagrams of the embodiment shown in FIG. 1 in a voltage applied state. 1... Non-doped GaSb layer, 2... Non-doped G
aSb layer, 3... Non-doped InAs layer, 4... Non-doped AfflSb layer, 5... Non-doped GaSb
layer, 6- n-type InAs substrate, 7-.-n-type InAs
Layer, 8... n-type InAs layer, 9, 10... electrode.

Claims (1)

[Claims] A second semiconductor layer having an electron affinity larger than the sum of the electron affinity of the first semiconductor layer and the forbidden band width is provided on the first semiconductor layer; a third semiconductor layer having a larger electron affinity than that of the third semiconductor layer; a fourth semiconductor layer having an electron affinity smaller than that of the third semiconductor layer; A fifth semiconductor layer is provided on the fourth semiconductor layer, and the sum of electron affinity and forbidden band width is smaller than the electron affinity of the third semiconductor layer, thereby forming at least one quantum well. A tunnel diode type semiconductor device.