JPH036672B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thyristor, which is a device at the limit of miniaturization and speeding up of semiconductor devices, and which controls the potential distribution in front of the cathode by the electrostatic induction effect of the control electrode and controls the tunnel injection current. .

Conventionally, thyristors whose operating principle is carrier injection amount control include thyristors with a pnpn structure and electrostatic induction thyristors (hereinafter referred to as SI thyristors). In a pnpn type thyristor, the voltage of the base electrode, which is the control electrode, controls the potential of the base via the base resistor, thereby controlling the amount of minority carriers flowing from the cathode. On the other hand, in the SI thyristor,
The channel region through which current flows is almost or completely depleted, and the channel potential is controlled by capacitive coupling with the voltage of the gate electrode, which is a control electrode, thereby controlling the amount of carriers injected from the cathode region. In any thyristor, the current flowing across the potential barrier is controlled by thermal energy. Therefore, although not so much, there is a carrier accumulation effect between the potential barrier and the cathode, which is one of the factors that limits the speed during ultra-high-speed operation.

The object of the invention is to provide a thyristor which almost completely eliminates these carrier accumulation effects and which operates at extremely high speeds.

The present invention will be described in detail below with reference to the drawings.

First, we will discuss the tunnel current when reverse bias is applied to a p ⁺ n junction diode. The expression for direct transition type tunnel current density is given by the following equation.

However, q: unit charge, m ^* : effective mass, h=
h/2π: Planck's constant divided by 2π, ε _g : band cap, V _a : applied voltage, and E is the maximum electric field of the p ⁺ n junction, E = {2qN _D (V _a +V _bi )/ε _s } ^1/2 ...(2) is given. Here, N _D is the impurity density in the n region, ε _s is the dielectric constant of the semiconductor, and V _bi is the diffusion potential of the p+n junction. The reverse applied voltage V _a of the reverse tunnel current density of the p+n junction given by equations (1) and (2)
The dependence is shown in Figure 1.

FIG. 1 shows the results of calculations using GaAs as the semiconductor material. Therefore, ε _q =1.43eV, ε _s =10.9ε _p . ε _p is the permittivity of vacuum.

m ^* =(1/me ^* +1/mlh ^* ) ^-1 , m ^* =0.068m _p , mlh ^* =0.12m _p .
m _p is the mass of the free electron. In FIG. 1, the current density is shown as a solid line and the electric field strength is shown as a dotted line.
N is the impurity density in the n region. As N becomes larger, the depletion layer width becomes narrower and the electric field E becomes larger, so that the current density becomes larger. For example, N=3
At ×10 ¹⁸ cm ^-3 , a current density of 3 × 10 ³ A/cm ² can be obtained at a voltage of 1V.

The thyristor of the present invention has a structure in which the tunnel current obtained as shown in FIG. 1 is controlled by the gate and anode voltages, which are control electrodes.

FIG. 2 shows the cross-sectional structure of the thyristor of the present invention. P ⁺⁺ region 11 is a cathode region, p ⁺ region 14 is an anode region, p ⁺ region 21 is a gate region, and 21' is a gate electrode, which controls the potential distribution of n ⁺ region 12 and n region 13, which serve as current paths. There is. 16 is an insulator, 11' is a cathode electrode, and 14' is an anode electrode. The impurity density of each region depends on the gate-to-gate spacing, but p ⁺⁺ cathode region 11: 5 × 10 ¹⁹ to 1 × 10 ²¹ cm
^-3 , n ⁺ 12: 5 × 10 ¹⁷ ~ 1 × 10 ¹⁹ cm ^-3 , n13: 1 ×
10 ¹⁴ ~ 1 x 10 ¹⁷ cm ^-3 , p ⁺ 14: 1 x 10 ¹⁸ - 5 x 10 ²⁰ cm
^-3 , p ⁺ 21: ^{10 18} to 5×10 ²⁰ cm ^-3 . n ⁺ 12, n13
The impurity density in each region is made higher as the gate-to-gate interval is shorter and as the cathode-anode interval is shorter. The gate-to-gate spacing may be, for example, from 2 μm or less to about 1000 Å, and the cathode-anode spacing may be thicker, for example, from 1000 Å to about 2 to 3 μm for ultrahigh speed applications. A cut-off state is achieved by applying a reverse voltage to the gate, and a conductive state is achieved by applying a zero potential to the gate or forward voltage. FIG. 3 shows the potential distribution in the cathode-anode direction with a positive voltage applied to the anode. a
is the potential distribution when a positive voltage is also applied to the gate to make it conductive, and b is the potential distribution when the gate is at zero potential (the cathode is at the same potential) or negative potential when it is cut off. In case a, a positive voltage is applied to the gate, so the potential gradient in front of the source becomes steep, and in case b, it becomes more gradual due to the gate voltage. The electric field E determined by this gradient is large at a, so a tunnel current flows, and at b, E
is small, so no tunnel current flows. As shown in Figure 3, the potential distribution of the channel, which is a current path, is controlled by capacitive coupling between the gate and cathode and between the gate and anode, that is, the electrostatic induction effect, and the tunnel current from the cathode is controlled.
Thyristor of the present invention, Static Induced Tunnel Thyristor:
SITT). If you want a large amount of tunnel current to flow, the higher the impurity density in the n ⁺ 12 region, the better.
Also, the thinner the thickness, the better. For example, the thickness is 0.2μ
It is 0.03 μm from m. When the thickness of the n ⁺ 12 region becomes thinner, the gate-to-gate spacing also needs to be narrowed. This is to more effectively control the entire surface of the channel to allow current to flow. For example, from 1 μm to 0.1 μm.

The thyristor of the present invention can be constructed not only of a junction gate type but also of an insulated gate and a shot gate type.

So far, we have explained a thyristor with a structure in which the cathode region and anode region are composed of high impurity density regions of the same conductivity type, but when the cathode region and anode region are composed of high impurity density regions of opposite conductivity type, A thyristor that takes advantage of the spirit of the present invention can be formed.

So far, we have basically explained one gate electrode that controls tunnel injection. Of course, it also includes divided gates. By providing a plurality of tunnel injection control gate electrodes and selecting the gate to which a control voltage is applied, a functional operation can be performed.

There are cases in which electrons tunnel-injected from the cathode travel in the travel region up to the anode by drifting, and cases in which they travel while being gradually accelerated with almost no scattering. Both of these appear
It is determined by the relationship between the mean free path through which electrons are scattered and the distance in the traveling space. If the traveling space distance is sufficiently long compared to the free path, the vehicle will drift. Otherwise, the vehicle will travel gradually at higher speeds due to the initial velocity and electric field. It is said that the free path of GaAs is several times longer than that of Si. Therefore,
The latter electron movement is more likely to appear in GaAs.

When electrons travel with less scattering, their traveling speed increases, and the upper limit frequency determined from the traveling time becomes extremely high.

In the embodiments so far, it has been described that the impurity density in the cathode where tunnel injection occurs and the region directly adjacent to the cathode is spatially uniform; however, it is not necessarily necessary that the impurity density be uniform. It is also possible to increase the tunnel injection efficiency by increasing the impurity density where the strongest tunnel injection is desired.

It goes without saying that the semiconductor device of the present invention is not limited to the embodiments described here. Of course, a structure in which the conductivity type is reversed may also be used. In any case, any semiconductor device may be used as long as it has a structure in which carriers are injected from the cathode by tunnel injection and the amount of injection is controlled by the electrostatic induction effect of the gate voltage and the anode voltage. In order to efficiently cause tunnel injection, the impurity density should be high. Moreover, the semiconductor device of the present invention is essentially a miniaturized device because this region is depleted and the potential distribution is controlled by capacitive coupling. It is ideal for not only individual devices but also ultra-high-density, ultra-high-speed integrated circuits. The smaller the dimensions of the device, the more effective it is. Moreover, since carriers are directly injected through tunnels from the high impurity density region,
The effect of carrier accumulation near the cathode is extremely small, making it extremely suitable for high-speed operation.

Here, we have shown an example in which the cathode region is formed in a high impurity density region, but of course it is also possible to make the cathode a metal or silicide, create a shot junction, and create a steep potential gradient in front of the shot junction to cause tunnel injection. be.

The semiconductor device of the present invention can be manufactured using conventionally known manufacturing techniques.

[Brief explanation of the drawing]

Figure 1 shows the results of calculations using GaAs as the semiconductor material, Figure 2 is a cross-sectional view showing an embodiment of the present invention, and Figure 3
The figure shows the potential distribution in the cathode-anode direction, where a indicates a conductive state and b indicates a blocked state.

Claims (1)

[Scope of Claims] 1. A first conductivity type semiconductor having a low impurity density and a high impurity density and having a conductivity type opposite to the second conductivity type and serving as a channel on one main surface of a second conductivity type semiconductor having a high impurity density and serving as an anode region. , a semiconductor region of a second conductivity type with a high impurity density is provided as a cathode region in contact with a semiconductor region of a first conductivity type with a high impurity density of the channel, and a semiconductor region of a second conductivity type with a high impurity density is cut in a convex shape from the cathode region to a low impurity density region of the channel. A tunnel injection control thyristor that includes control regions on both side walls and controls tunnel injection current generated in the cathode region and the high impurity density region of the channel. 2. The tunnel injection control thyristor according to claim 1, wherein the control electrode is an insulated gate. 3. The tunnel injection control thyristor according to claim 1, wherein the control electrode is a junction type gate. 4. The tunnel injection control thyristor according to claim 1, wherein the control electrode is a shot key gate. 5. The tunnel injection control thyristor according to any one of claims 1 to 4, characterized in that a plurality of the control electrodes are provided.