JPH01214164A - resonant tunneling 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] Regarding a transistor having a resonant tunneling barrier between the emitter and base junction, the present invention relates to a transistor having a resonant tunneling barrier between the emitter and base junction for the purpose of improving current gain and reducing base resistance. death,
A resonant tunneling transistor configured to generate a resonant tunneling effect and inject electrons into the base by applying a voltage between the emitter and the base, in which at least the base layer is formed of a 1nAs layer, and the resonant tunneling barrier is formed of InAtAs1. It is formed from an InGaAs layer.

[Industrial application field]

The present invention relates to resonant tunneling transistors, and more particularly to transistors having a resonant tunneling barrier between emitter and base junctions.

A hot electron transistor (HET: Hot El) shortens the transit time by using hot electrons (hot electrons) that are not in equilibrium with the semiconductor crystal lattice as carriers that travel through the transistor channel layer.
The resonant tunneling pot electron transistor (RHE) injects electrons into the base by the resonance tunneling effect.
T: Resonant-tunneling I
IET) has attracted attention as an ultra-high-speed, new-function transistor, and is being developed as a future device.

In order to further improve the performance of this RHET, we aim to increase the speed by reducing parasitic resistance such as base resistance, and to ensure stable operation when the circuit is assembled, the collector current that is the output and the base that is the signal It is necessary to have a large ratio to the current (current gain).

[Conventional technology]

FIG. 3 shows a structural cross-sectional view of an example of a conventional RHET. In the figure, 1 is a non-doped InP substrate, 2 is an InGaAs layer forming a collector region, and 3 is a non-doped InP substrate.
tGaAs layer, 4 is InGa forming the base region
As layers 5 and 7 are each made of non-doped InAtAs.
MW, 6 is a non-doped InGaAs layer, and 8 is an InGaAs layer forming an emitter region. Further, E is an emitter electrode, B is a base electrode, and C is a collector electrode.

The InGaAs layers 2 and 8 are each doped with an n-type dopant such as Si (silicon) at a high concentration (1×10+sυ−3), and have a film thickness of about 3000 layers. In addition, the film thickness of InAtGaAsff3 is, for example, 2000
The thickness of the GaAs layer 4 is 500 mm, and n
In addition, the thickness of the InAtAs FJs 5 and 7 is 30 nm each, and the thickness of the InGaAs layer 6 is 20 nm, which form a resonant tunneling barrier.

To explain the operation of the above-mentioned RHET, first, as long as no voltage is applied between the emitter and the base, no electrons are injected into the base and no collector current flows. Next, when a suitable voltage is applied between the emitter and the base, electrons are injected into the base due to the resonant tunneling effect. Electrons injected into the base become hot electrons with a high initial velocity.

FIG. 4 shows the energy band diagram of the conduction band of the RHET in FIG. 0.55 eV, and 9 is the i I n At A
It shows the resonant tunneling barrier of the emitter consisting of the s layer 5.7 and the i-InGaAs layer 6, and 10 is the height of the collector barrier, which is about 0.25 eV here.

Further, EF is the Fermi level.

The hot electrons pass through the base at an extremely high speed, cross the collector barrier 10, and reach the collector, so that a collector current flows. Electrons that lose energy due to scattering or the like in the base and cannot cross the collector barrier 10 become base current.

If excessive voltage is applied between the emitter and the base, the condition for resonant tunneling is violated and the collector current decreases.

Compared to other conventional bipolar transistors and unipolar transistors, the RHET based on such an operating principle can achieve eight speeds and reduce the number of elements required for an integrated circuit. In addition, R) IET with the structure shown in Fig. 3 has a separation energy of 0.30 that of GaAs.
Since the InGaAs layer 4 with o, 5 sev, which is larger than eV, is used as the base layer, and the InALGaAs layer 3 is used to lower the height of the collector barrier 10, the emitter current gain hFε exceeds 10. The value is obtained.

[Problem to be solved by the invention]

However, in the above conventional RHET using the lnGaAs layer 4 as the base layer, even though the separation energy between the valley and the L valley is larger than that of GaAs, it is only 0.55 e Electrons with an energy of
Electrons with only the following energies are collector barrier 1
It is reflected at 0 and cannot reach the collector.

Therefore, in the conventional RHET described above, the energy range in which electrons can reach the collector is 0.295 (=0.55
-0.255) eV and narrower R for larger current gain
The realization of HET was required.

In addition, in the conventional RHET, the I nA of the collector barrier 10
Since the tGaAs layer 3 is a quaternary system, there is also a problem that the fIIIll property is not good.

The present invention has been made in view of the above points, and it is an object of the present invention to provide a resonant tunneling transistor that makes it possible to improve current gain and reduce base resistance.

[Means to solve the problem]

In the resonant tunneling transistor of the present invention, at least the base layer is formed of InAsJl, and the resonant tunneling barrier is formed of 1 nALAsI and InGaAsff.

It may or may not have a collector barrier,
If so, the collector barrier is formed of an InGaAs layer.

[Effect]

InAs has "separation energy between the valley and the L valley that is greater than or equal to o, aev, which is 0.5 of that of InGaAs.
58V, the present invention using InAs1i as a base layer is less susceptible to trough n failure. Furthermore, since the mobility of 1 nAs is 1.5 times greater than that of InGaAs, the base resistance is small.

Furthermore, in the case of a resonant tunneling transistor (in this case a resonant tunneling hot electron transistor) having a collector barrier, the collector barrier is InGaA.
Since it is formed of the s-layer, it is less susceptible to valley scattering at the collector barrier than a conventional transistor whose collector barrier is InAtGaAs.

〔Example〕

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

In the figure, the same components as in FIG. 3 are designated by the same reference numerals, and their explanations will be omitted. In FIG. 1, 12 is InGaA
s1i, 13 is InAsjlt, 14 is 1-1nGaA
sl, 15 is a base layer and is a T(7) InAs layer.
They are sequentially stacked on a P substrate 1. InAs[i15
On top are a non-doped InAtAs layer 5.7 and a non-doped InG layer constituting an emitter resonant tunneling barrier.
an aAs layer 6 is formed.

The above 1nGaAsii12 is doped with an n-type dopant such as 3i at a high concentration (1X1019C11''3), and its film thickness is said to be 2500.
The As layer 13 also has a carrier concentration similar to that of the InGaAs layer 12, but is formed to have a thickness of 500 nm.

InGaAs Ei 14 is provided to constitute a collector barrier, and is non-doped and has a film thickness of 2000 mm.
formed by people. Furthermore, I nA as a base layer
The sAs layer 1 is doped with an n-type dopant at a concentration of ixiomα, and its film thickness is 200 to 500 nm.
considered to be a person.

In a RHET with such a structure, the energy band diagram of the conduction band when an appropriate voltage is applied between the emitter and the base is shown in Figure 2. As a result, the InAs layer 17 has a "trough" (shown as a solid line in FIG. 2).
The separation energy between the G
It can be increased by 0.258V compared to o, 5sev by aAsJI4. Therefore, hot electrons are less susceptible to scattering into valleys than in the past.

In addition, the height of the collector barrier 17 is the same as that of the InGaAs layer 14.
Therefore, it becomes 0.25 eV, and the conventional InAtGa
It is comparable to that of AsFJ3. Therefore, InGa
The separation energy between the As IF514 F valley (shown by the solid line in FIG. 2) and the valley (shown by the broken line in FIG. 2) is 0.55 eV.

According to this embodiment, the range in which electrons can reach the collector is 0.55 eV, which is much larger than the conventional 0.295 eV. The rate of reaching the collector will increase.

Therefore, according to this embodiment, the emitter current gain hFε can be improved to about twice that of the conventional one, and even with a base width of 250 people,
30" or more can be achieved, and base resistance, sheet resistance,
Contact resistance is reduced and high speed performance is achieved. Also,
Since the collector-base voltage can be increased, a large operating margin can be achieved.

It should be noted that the present invention is not limited to the above-mentioned embodiments, but is based on a resonant tunneling bibolar transistor (RB T
: Resonant-tunnelingBip
polarTransistor).

In other words, RBT differs from RHET only in that the base layer is doped with a p-type dopant such as beryllium (Be) to a high mi, and that a collector barrier is not required due to the withstand voltage of the base and collector. , InA
The base layer may be formed from S, and the resonant tunneling barrier may be formed from lnA1 As and InGaAs.

〔Effect of the invention〕

As described above, according to the present invention, the energy range in which electrons can reach the collector can be expanded, so the emitter current gain can be increased to about twice that of the conventional one, and the base resistance, sheet resistance, and contact resistance can be reduced. Since the RHET can be lowered, the high speed can be increased, and the operating margin can be further expanded. Furthermore, since the collector barrier is a ternary system, the controllability can be improved compared to the conventional RHET.

[Brief explanation of the drawing]

FIG. 1 is a structural sectional view of one embodiment of the present invention, and FIG.
Figure 3 is a structural sectional view of a conventional example, and Figure 4 is an energy band diagram of the conduction band of the RHET shown in Figure 3. In the figure, 1 is a 1-1nP substrate, 5.7 is a 1-InAtAs layer, and 6 is! -1nGaAs layer, 8.12 is n''-1nGaAs layer, 9 is a resonant tunneling barrier, 13 is n''-InAs layer, 14 is i-1nGaAs layer, and 15 is n-1nAsll. Figure 1 Early Z map RHET/) Ukumisaki pxko: Metrusuno and Odenko I! Figure 2

Claims (2)

[Claims] (1) A resonant tunneling transistor having a resonant tunneling barrier between the emitter and the base junction, and having a configuration in which a voltage is applied between the emitter and the base to cause a resonant tunneling effect and inject electrons into the base, and at least the base The layer is formed of an InAs layer (15), and the resonant tunneling barrier is formed of an InAlAs layer (5).
, 7) and an InGaAs layer (6). (2) A resonant tunneling transistor having a collector barrier, the collector barrier being an InGaAs layer (
14. The resonant tunneling transistor according to claim 1, wherein the resonant tunneling transistor is formed by step 14).