JPH01214159A - Hot electron transistor - Google Patents

Abstract

PURPOSE:To reduce base resistance and improve breakdown strength between C and B, by adjusting the doped amount of a base and causing a difference in prescribed energy levels to be around or above the height of a collector barrier, and by installing a no-added spacer layer between base and collector barriers. CONSTITUTION:An n-type InGaAs base thin layer 9 is provided on an InP substrate 1 through an n<+>-type InGaAs collector 2, an i-type InAlGaAs 3, an i-type InGaAs spacer 8. An i-type InAlAs 5 are put on the thin film layer 9. Assume that the amount of doping to a composition of the base layer 9 is 9X10<18>cm<-3>. In such a case, when a thermoelectron transistor is operated, Fermi levels EF of the base 9 and spacer 8 are shown as chain lines I. In view of the doped amount in the base 9, EC-EF of the base is 0.39eV and it is higher than the height of a collector barrier: E=0.27eV which is obtained by the spacer 8 and yet, sheet resistance exceedingly decreases. The spacer 8 belongs to an i-type and when EC-EF=0.01eV, it is smaller than EC. Thus, breakdown strength between C and B can be improved.

Description

[Detailed Description of the Invention] [Summary] A hot electron transistor that converts electrons injected into a base into hot electrons (hot electrons) with high kinetic energy and travels.・Aiming to improve the breakdown voltage between the bases, electrons in the emitter layer are made to pass through the emitter barrier by tunneling effect and injected into the base layer to become hot electrons with high kinetic energy, and the hot electrons are transferred to the collector layer. In the hot electron transistor, the doping amount of the base layer is set to EC-
EF (where EC is the level at the bottom of the conduction band; EF is the Fermi level) is set to a value near the height of the collector barrier or a value exceeding the collector barrier, and the base layer and the collector are A non-doped or substantially non-doped spacer layer is interposed between the barrier and the barrier.

[Industrial application field]

The present invention relates to a pot electron transistor, and more particularly to a hot electron transistor in which electrons injected into a base are converted into hot electrons (hot electrons) having high kinetic energy and travel.

Although recent advances in semiconductor manufacturing technology have been remarkable, there are limits to miniaturization by lithography, and interconnect delays have become a problem with higher integration. In order to solve these problems, we shortened the transit time by using hot electrons, which are not in equilibrium with the semiconductor crystal lattice, as carriers traveling through the transistor channel layer, and we also added new functions to the transistor and increased the number of elements. Pot electron transistors (IIET: Ho
t Electron Transistor) is attracting attention.

Such HETs are required to further improve current gain and reduce base resistance.

[Conventional technology]

FIG. 3 shows a structural sectional view of an example of a conventional HET. In the figure, 1 is a non-doped InP substrate, 2 is an InGaAs layer 4 forming a collector region, and 3 is a non-doped InP substrate.
At GaAs layer, 4 is 1nQa forming the base region
5 is an As layer, 5 is a non-doped InAjAs layer, and 6 is an InGaAs layer 4 forming an emitter region. Also, E
is an emitter electrode, B is a base electrode, and C is a collector N pole.

The InGaAs layers 2 and 6 are each doped with an n-type dopant such as Si (silicon) at a high concentration (1×10!9♂3), and have a film thickness of about 3000 layers. Also In□, 53 (AjO, 5Gag, 5) 0.47A
The film thickness of InGaAsff3 (7) is, for example, 2000A t', InGaAs11417) film thickness G, t 250A, and the n-type dopant is usually doped at a concentration of 1 x 10'' as-3. Furthermore, the film thickness of lnALAsff15 is 20OA.

Next, the operation of the above HET will be explained.

First, when no voltage is built up between the emitter and the base, no electrons are injected into the base and no collector current flows. Next, when a voltage is applied between the emitter and the base, the energy band diagram of the HET shown in FIG. 3 becomes as shown in FIG. 4.

That is, the electrons in l nGaAsjl15 in the emitter region become I nAj ASIIi5 due to the tunnel effect.
■nGaASl of the base layer passes through the emitter barrier of height O, 55 eV due to ! Injected into I4. The electrons injected into the base H (InGaAs layer 4) absorb the potential energy of the potential difference between the emitter and the base,
They are converted into kinetic energy and become hot electrons with high kinetic energy, which pass through the thin base layer at ultra-high speed and reach a height of 0 due to Iy+ At GaAs1i3.
．． 27eV (7) ml It reaches the collector region (InGaAs layer 2) beyond the collector barrier.

HETs based on this operating principle have a thin base layer, so they are less susceptible to scattering, and can be expected to transport electrons in a parisistic manner. As a result, the base running time may become extremely short. Electrons that have lost energy due to scattering in the base cannot cross the collector barrier and become base current. Therefore, to improve the current gain, first of all base II
need to be reduced.

[Problem to be solved by the invention]

However, since the current gain of HET is small, if the base layer (InGaAs layer 4) is made thinner in order to reduce the base current and improve the current gain, the base resistance will increase and the transit time of carriers will increase. It ends up.

Therefore, as a method to reduce the base resistance and improve the current gain, the base width was changed to about 250 Atl<Lr, and the doping I of the base layer (InGaAs layer 14) was changed to the normal l
From about X10"α-3 to, for example, 3x10"c114,
Furthermore, it is conceivable to increase the size to three 9x10".

If the doping amount of the base is increased as above (3X10), the base sheet resistance Rs will be 10
If the doping amount is further increased to 9×10” am4, the sheet resistance Rs can be further reduced to about 110Ω.

However, on the other hand, the doping amount of the base layer is 3×10”×
The value increased to 4 is the difference between the bottom level EC of the conduction band in the base layer and the Fermi level EF (EC - EF).
becomes as large as O-20eV, and the doping amount is increased to 9X 10”
tx-”, the above (EC-E
F) becomes 0.398V, and the collector barrier height Δ
There was a point where the voltage exceeded EC (in this case (+, 27e V)), the withstand voltage between the collector and base disappeared, and the HET could no longer operate normally.

The present invention has been made in view of the above points, and it is an object of the present invention to provide a hot electron transistor with reduced base resistance and improved breakdown voltage between the collector and base.

[Means to solve the problem]

In the hot electron transistor of the present invention, the doping amount of the base layer is set as EC-EF (where EC is the bottom level of the conduction band and Ep is the Fermi level) as the collector barrier.
The base layer is made large enough to have a value close to that of the collector barrier or exceeds the collector barrier, and a non-doped or substantially non-doped spacer layer is interposed between the base layer and the collector barrier.

[Effect]

In a hot electron transistor in which electrons in the emitter layer are made to pass through the emitter barrier by tunneling effect and injected into the base layer to become hot electrons with high kinetic energy, and the hot electrons reach the collector layer, the doping amount of the base layer is set as above. By making it a dog like this, the base resistance can be reduced.

Furthermore, since the spacer layer is non-doped or set to have an S degree extremely close to non-doped, the EC-EF value at the interface between the base layer and the collector barrier can be made 4 minutes smaller than the height of the collector barrier.

(Example) FIG. 1 shows a structural sectional view of an embodiment of the present invention.

In the figure, the same components as those in FIG. 3 are designated by the same reference numerals, and their explanations will be omitted. In FIG. 1, 8 is a spacer layer made of i -1nGaAs. Further, 9 is a base layer made of nInGaAs.

That is, this embodiment differs from the NET shown in FIG. 3 in the spacer layer 8 and the n-InGaAs layer 9, but the other structures are the same. n-1nGaAsl19 is 1X10"cx"9 with the normal concentration of n-type dopant in S1'@
It is doped with a considerably large amount of doping, 9×10” am-3, and its film thickness is approximately 200 mm.

Further, the spacer ms interposed between the n-InGaAs layer 9 as the base layer and the i-1nAt GaAs layer 3 for forming the collector barrier is made of non-doped InGaAs, and the spacer ms is made of non-doped InGaAs. The thickness is said to be, for example, 50 people.

FIG. 2 shows an energy band diagram during operation of the HET of this embodiment having such a structure. According to this embodiment, the base layer (
EF in n-1nGaAs layer) 9 and spacer layer 8
is as shown in FIG. 2 by a chain of dots. That is,
The doping of the base layer (n-InGaAs layer) 9 is 9X
10" ax, so the value of EC-EF is 0.3
9 V, and the collector barrier ΔEC is 0.27
Although it is more human than eV, the sheet resistance Rs is 110Ω, which can be significantly reduced compared to the usual 1000Ω.

On the other hand, since the spacer 118 is non-doped, its F
Since the value of C-EF is 0.01 eV, which is 0.26 eV smaller than the collector barrier height ΔEC of 0.27 eV, the breakdown voltage between the collector and emitter is significantly improved compared to the conventional one.

Note that the spacer layer 8 has a doping amount of 5 x 10” cm.
It may be set to a value close to non-doped, such as ', in which case EC - EF = 0.05 eV.

Further, the present invention is applicable not only to HET but also to emitter barriers such as I n A t A s / I n G a A
The present invention can also be applied to a resonant tunneling hot electron transistor having a double-barrier pillar structure.

〔Effect of the invention〕

As described above, according to the present invention, the doping ratio of the base layer can be increased compared to the conventional method, so that the carrier transit time can be shortened by reducing the base resistance, and the current gain can also be improved. Furthermore, the spacer layer significantly improves the withstand voltage between the collector and base, and has the advantage of providing good current-voltage characteristics.

[Brief explanation of the drawing]

FIG. 1 is a structural sectional view of one embodiment of the present invention, and FIG.
FIG. 3 is a structural sectional view of a conventional example, and FIG. 4 is an energy band diagram of the HET shown in FIG. In the figure, 1 is a 1-1np substrate, 3 is an i-InA1 GaA that forms a collector barrier.
SJi, 6 is the emitter FJ (n” -1nGaAsJ
1), 8 is a spacer layer, and 9 is a base layer (n-InGaAs layer). Fig. 1 Rod 1 sound a/) HET knee 1 N-bere v'm Fig. 2 Fig. 3 Early 3/) NET-)

Claims (1)

[Claims] Electrons in the emitter layer (6) are caused to pass through the emitter barrier by a tunnel effect and injected into the base layer (9) to become hot electrons with high kinetic energy, and the hot electrons are converted into hot electrons with high kinetic energy. ), the doping amount of the base layer (9) is set so that E_C - E_F (where E_C is the bottom level of the conduction band and E_F is the Fermi level) is the height of the collector barrier (ΔE_C). A non-doped or substantially non-doped spacer layer (8) is provided between the base layer (9) and the collector barrier. hot electron transistor.