JPH02202059A - Semiconductor device - Google Patents

Abstract

PURPOSE:To secure the breakdown strength between a base and a collector and to enable a semiconductor device of this design to operate at a high speed and to be improved in current amplification factor by a method wherein an intrinsic semiconductor layer, which is higher than a barrier layer in electron affinity, is provided between the barrier layer and a second semiconductor layer. CONSTITUTION:An intrinsic semiconductor layer 8 whose electron affinity is larger than that of a collector barrier layer 6 is provided between a collector barrier layer 6 and a collector layer 4. The sum of the thickness of the collector barrier layer 6 and the intrinsic semiconductor layer 8 is equal or so to that of a conventional collector barrier layer, so that the thickness of the collector barrier layer 6 is made smaller by the thickness of the intrinsic semiconductor layer 8. Therefore, a time required for hot electrons to pass through the collector barrier layer 6 whose electron affinity is small becomes short. By this setup, the breakdown strength between a collector and a base can be secured, and a semiconductor device of this design can be improved in operation speed and current amplification factor.

Description

[Detailed Description of the Invention] [vA Required] Regarding semiconductor devices, especially hot electron transistors, it is possible to increase the operating speed and improve the current amplification factor while ensuring the withstand voltage between the base and the collector. The object of the present invention is to provide a semiconductor device having a barrier layer between a first and a second semiconductor layer, in which a barrier layer is provided between the barrier layer and the second semiconductor layer. The structure is such that a genuine semiconductor layer having a large electron affinity is provided.

[Industrial Field of Application] The present invention relates to a semiconductor device, and particularly to a hot electron transistor.

[Prior Art] A conventional hot electron transistor will be explained using FIG. 4.

FIG. 4(a) is a cross-sectional view showing a cross section of a conventional hot electron transistor, and FIG. 4(b) is a cross-sectional view of a conventional hot electron transistor.
A band diagram showing the energy level Vc of the bottom of the conduction band corresponding to This is a band diagram showing the energy level Vc at the bottom of the conduction band corresponding to figure (c).

In a conventional hot electron transistor, for example, n-type GaAs is placed on a substrate 10 made of i-type GaAs.
Collector layer 4 consisting of 1-type A1GaAs collector barrier layer 6a, base layer 2 consisting of n-type GaAs,
An emitter barrier layer 12 made of i-type AN GaAs and an emitter layer 14 made of n-type GaAs are laminated,
It has a vertically laminated multilayer heterostructure.

In this way, while GaAs is used for the emitter layer 14, base layer 2, and collector layer 4, respectively, the emitter barrier layer 12 and the collector barrier layer 6a have a smaller electron affinity than GaAs. Aj
GaAs is used, as shown in FIG. 4(b),
It forms an energy barrier.

and a collector layer 4, a base layer 2, and an emitter layer 1
4 have a collector electrode 16 and a base tiis, respectively.
, and an emitter t[120.

In addition, in such a hot electron transistor, in order to increase the withstand voltage between the base and collector, as shown in FIGS. Since the energy level Vc at the bottom of the conduction band when a voltage is applied needs to have a gentle slope, the thickness of the collector barrier layer 6a is quite thick, for example, about 2000 layers.

[Problems to be Solved by the Invention] As described above, in the conventional hot electron transistor described above, in order to ensure the withstand voltage between the base and the collector, it is necessary to make the collector barrier layer 6a, which has a small electron affinity, considerably thick. was there.

For this reason, hot electrons are transferred to the collector barrier layer 6.
There is a problem that the time required to pass through a becomes longer and the operating speed of the transistor becomes slower.

In addition, when the applied voltage between the base layer 2 and the collector layer 4 is low or in a weak reverse bias state, there was an interlayer in which the hot electron transport efficiency decreased and the current amplification factor decreased.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a semiconductor device that can increase operating speed and improve current amplification factor while ensuring a base-collector breakdown voltage.

[Means to solve the problem] FIG. 1 is a diagram explaining the principle of the present invention.

The semiconductor device shown in FIG. 1(a) has a collector barrier layer 6 with low electron affinity between the base layer 2 and the collector layer 4, and a collector barrier layer 6 between the collector barrier layer 6 and the collector layer 4. It has a true semiconductor layer 8 having a higher electron affinity than the barrier layer 6.

The total thickness of the collector barrier layer 6 and the genuine semiconductor layer 8 is approximately the same as the thickness of the conventional collector barrier layer. That is, the thickness of the collector barrier layer 6 is reduced by the amount of the genuine semiconductor 8 present.

[Function] The band diagram of the energy level Vc at the bottom of the conduction band when a constant voltage is applied between the base layer 2 and the collector layer 4 in Fig. 1(a) is shown in Fig. 1(b). show.

The voltage applied between the base layer 2 and collector layer 4 is
It is applied not only to the collector barrier layer 6, which has a low carrier concentration, but also to the genuine semiconductor layer 8, which has a similarly low carrier concentration. Since the total thickness of the collector barrier [6 and the genuine semiconductor layer 8 is approximately the same as the thickness of the conventional collector barrier layer, the electric field strength applied to the collector barrier layer 6, in other words, the energy level at the bottom of the conduction band Vc The slope of the collector barrier layer 6 is approximately the same as that of the prior art, and therefore the appearance of the band of the collector barrier layer 6 near the boundary with the base layer 2 is also the same as that of the prior art.

The number of electrons injected from the base layer 2 to the collector layer 4 is determined by the shape of the band of the collector barrier layer 6 near the boundary with the base layer 2, so that the same base-collector breakdown voltage as before is ensured. Ru.

On the other hand, the speed of hot electrons passing between the base layer 2 and the collector layer 4 increases as they enter the true semiconductor layer 8, which has a large electron affinity, from the collector barrier layer 6, which has a small electron affinity. Furthermore, since the effective mass of carriers in semiconductors, which generally have a large electron affinity, becomes small, the traveling speed of hot electrons is further accelerated. In this way, the time required for hot electrons to travel from the base layer 2 to the collector layer 4 is shortened.

Furthermore, the hot electrons that have passed through the collector barrier layer 6 from the base layer 2 and reached the true semiconductor layer 8, which is thinner than the conventional one, reach the collector layer 4 even if they lose energy due to scattering or the like. The hot electron transport efficiency increases when the voltage applied between the collectors is low or when the voltage is reverse biased.

[Example] The present invention will be specifically described below based on an illustrative example.

FIG. 2(a) is a cross-sectional view showing a cross section of a semiconductor device according to an embodiment of the present invention, and FIG. 2(b) shows the energy level Vc at the bottom of the conduction band corresponding to FIG. 2(a). This is the band diagram shown.

As shown in FIG. 2(a), the semiconductor device according to this embodiment has a substrate 10 made of, for example, l-type GaAs,
Collector layer 4 made of type GaAs. Authentic semiconductor layer 8 made of 1 type GaAs, collector barrier layer 6 made of l type AjGaAs, base layer 2 made of n type GaAs, l type A.
An emitter barrier layer 12 made of jGaAs and an emitter layer 14 made of n-type GaAs are stacked to form a vertically stacked multilayer heterostructure.

In this way, the emitter layer 14, the base layer 2, the collector layer 4, and the genuine semiconductor layer 8 are each made of, for example, GaAs, whereas the emitter barrier layer 12 and the collector barrier layer 6a are each made of GaAs. AJ with low affinity! It is made of GaAs and forms an energy barrier as shown in FIG. 2(b).

The thickness of the collector barrier layer 6 is 1000 nm, which is about half of the conventional thickness, and the thickness of the true semiconductor layer 8 is also 1000 nm.
008, and the thickness of the collector barrier layer 6 is thinner than the conventional one by the thickness of the genuine semiconductor 8.

In addition, a collector layer 4, a base layer 2, and an emitter layer 1
4 are provided with a collector electrode 16, a base electrode 18, and an emitter electrode 20, each made of A u /Cr.

In the semiconductor device according to this embodiment, when a voltage is applied between the base layer 2 and the collector layer 4, the total thickness of the collector barrier layer 6 and the genuine semiconductor layer 8 is 2000 mm compared to the conventional collector barrier layer. Since the thickness is approximately the same as that of the collector barrier layer 6, the band of the collector barrier layer 6 near the boundary with the base layer 2 exhibits the same appearance as in the conventional case. Therefore, it is possible to secure the same breakdown voltage between the base and the collector as in the conventional case.

Furthermore, when the hot electrons traveling between the base layer 2 and the collector layer 4 pass through the collector barrier layer 6 and enter the genuine semiconductor layer 8, the hot electrons pass through the collector barrier layer 6 and enter the genuine semiconductor layer 8.
Since the As layer is transferred to the l-type GaAs layer having a large electron affinity, the kinetic energy increases and the traveling speed becomes faster. And also, the effective mass of the electron is All GaAs
Since the GaAs medium is smaller than the GaAs medium, its traveling speed is further accelerated.

In this way, the travel time of hot electrons between the base layer 2 and the collector layer 4 can be shortened, and the operating speed of the semiconductor device can therefore be increased.

Furthermore, the hot electrons traveling between the base layer 2 and the collector layer 4 pass through the collector barrier layer 6, which is half as thin as the conventional one, and pass through the genuine semiconductor 71.
8, it can reach the collector layer 4 even if it loses energy due to scattering or the like. In this low bias state or reverse bias state between the diagonal base and the collector, the hot electron transport efficiency can be increased. Therefore, semiconductor equipment! The current amplification factor can be improved.

In the above embodiment, the thickness of the collector barrier layer 6 was set to 1000 nm, and the thickness of the genuine semiconductor layer 8 was set to 100 nm.
A, but for example, if the thickness of the collector barrier layer 6 is 500
The thickness of the true semiconductor layer 8 may also be set to 1500. The thinner the collector barrier layer 6 is, the more
The operating speed of a semiconductor device can be increased.

The limit is that the thickness of the collector barrier layer 6 becomes too thin, and even though the slope of the energy level Vc at the bottom of the conduction band of the collector barrier layer 6 is the same as that of the conventional one, the boundary with the base layer 2 The shape of the band of the collector barrier layer 6 in the vicinity, the shape of the so-called triangular potential, changes from the conventional one, and the number of electrons injected from the base layer 2 to the collector barrier layer 6 increases rapidly. When the thickness of the collector barrier layer 6 becomes thin, the breakdown voltage between the base and the collector deteriorates.

In addition, in the above embodiment, AjGaA is used as a barrier layer with a small electron affinity and a semiconductor layer with a large electron affinity.
Although a combination of InAjAs and GaAs was used, the combination is not limited to this, and InAjAs and InGaAs, InGaAj A
s and I nGaAs, Si and Ge, CdTe and HgCd
Te, etc. can be applied to almost all semiconductor devices having a barrier structure using a semiconductor heterojunction.

Next, the method for manufacturing the semiconductor device shown in FIG.
This will be explained using figures.

A collector 1 made of n-type GaAs is grown on a substrate 10 made of l-type GaAs using an epitaxial growth method.
4. Authentic semiconductor layer with a thickness of 1000 nm consisting of i-type GaAs 8, i-type A with a smaller electron affinity than GaAs
Collector barrier layer 6 made of AjGaAs with a thickness of 1000 nm, base layer 2 made of n-type GaAs, 2.1 type AjGaA
Emitter barrier layer 12 made of s and n-type GaAs
The emitter layers 14 consisting of the following are stacked in order to form a vertically stacked multilayer heterostructure (see FIG. 3(a)).

Next, a predetermined pattern of mask material 2 is applied on the emitter layer 14.
Using this mask material 22 as a mask, the emitter layer 14 and the emitter barrier layer 12 are selectively etched to expose the base layer 2 (see FIG. 3(b)).

Next, a mask material 24 having a predetermined pattern is formed again on the emitter layer 14 and the base layer 2, and the base layer 2, the collector barrier layer 6, and the genuine semiconductor layer 8 are selectively etched using the mask material 24 as a mask. , exposing the collector layer 4 (see FIG. 3(c)).

Next, on the collector layer 4, base layer 2, and emitter layer 14, a collector electrode f#116, a base electrode 18, and an emitter electrode 2 each made of Au/Cr are formed.
0 (see FIG. 3(d)).

In this way, the semiconductor device shown in FIG. 2 is manufactured.

[Effects of the Invention] As described above, according to the present invention, the total thickness of the collector barrier layer and the true semiconductor layer sandwiched between the base layer and the collector layer is equal to the thickness of the conventional collector barrier layer. By making it approximately the same, it is possible to ensure the same base-collector breakdown voltage as in the conventional case.

Since the collector barrier layer is thinner than before, a true semiconductor layer with a higher electron affinity than the collector barrier layer is provided, so the traveling speed of hot electrons traveling between the base and the collector becomes faster. The running time can be shortened, and the operating speed of the semiconductor device can therefore be increased.

Further, the transport efficiency of hot electrons can be increased in a low bias state or a reverse bias state between the base and the collector, and therefore the current amplification factor of the semiconductor device can be improved.

[Brief explanation of the drawing]

1 is a diagram illustrating the principle of the present invention; FIG. 2 is a diagram showing a semiconductor device according to an embodiment of the present invention; FIG. 3 is a process diagram showing a method for manufacturing the semiconductor device of FIG. 2; FIG. 4 is a diagram for explaining a conventional semiconductor device. In the figure, 2...Base layer, 4...Collector layer, 6.6a...Collector barrier layer, 8...
- Genuine semiconductor layer, 10...Substrate, 12...Emitter barrier layer, 14...Emitter layer, 16...Collector as pole, 18... ... Base electrode, 20 ... Emitter electrode, 22.24 ... Mask material. Collector layer Genuine semiconductor layer Figure 1, explanatory diagram of the principle of the present invention

Claims (1)

[Claims] In a semiconductor device having a barrier layer (6) between the first and second semiconductor layers (2) and (4), the barrier layer (
6) and the second semiconductor layer (4), an authentic semiconductor layer (8) having a higher electron affinity than the barrier layer (6).
A semiconductor device characterized by being provided with.