JPS61222166A - Transistor - Google Patents

Abstract

PURPOSE:To increase HFE extremely by constituting an emitter section and a collector section in a transistor by Si and organizing a base section by Ge. CONSTITUTION:An N-type Si wafer is used, and Ge is grown on the wafer through a MOCVD method. A P-type impurity is diffused to Ge. Si is grown through the MOCVD method, and an N-type impurity is diffused. Lastly, electrodes as an emitter, a base and a collector are formed through etching.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention provides silicon (Si) and germanium (Ge)
0 <Summary of the Invention> The emitter and collector parts of the transistor are made of Si, and the base part is made of Si. As a result, the HPE of the transistor becomes extremely large, and even an optical trigger can sufficiently increase the HPE to several tens.

<Prior Art> Conventional transistors are composed only of Si or Ge. The HFE of these transistors is about 102 at most.

<Problems to be solved by the invention> For example, in an optical coupler type power transistor, etc., even if a pace current of μA order is supplied in relation to the light receiving element, the HFE is about 102 as described above, and there is no sufficient output. Can't get current.

An object of the present invention is to provide a transistor with an extremely high HFE with a novel structure.

Means for Solving the Problems> The emitter and collector portions of the transistor are made of Si, and the base portion is made of Ge. That is, 5i-Ge
-3i structure transistor.

In the above structure, HFEαee (Vdv, -vac)/kT -0, -
The relational expression 9+(1) holds true. As will be described later, the conventional S
In the case of a transistor containing only i or Ge, Vdv=Vdc, and the above factor does not appear. Si − of the present invention
Transistors made of Ge-Si structure can achieve extremely high HFE according to the fafter described above, and in one prototype example, HFE can be extremely high.
I got something on the order of 0.

<Example> An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a diagram showing the Fermi level of an NPN transistor according to the present invention. The emitter section E and the collector section C are each made of Si and have N type conductivity. The base portion B is made of Ge and has P type conductivity.

Now, Vdc is considered to be 0.4v, and if the bandgap of Ge is 0.72eV (300K), the difference is 0.82eV. On the other hand, since the bandgap of Si is 1.09eV (800K), Vd v #1
．． 09-OJ2=0.77V.

Then, in the above relational expression +11, e(Vdv-Vdc)#0.77-0.4=0.87e
Therefore, HFEαe (4282°4/T) ・・・・・・・・・
...(2) becomes. Note that due to temperature changes, Vdv,
Vdc also differs, but S
Since i and Ge also change in almost the same way, the above relational expression (2
), the value of 6 (Vd v −Vd c ) can be considered to be almost constant.

By the way, 25 degrees Celsius (298 degrees K) and too degrees Celsius (878 degrees
K), HFE (25℃, αe14.4 HFE (100℃) αe11.5, considering that e = 2.2X10, this factor alone makes the HFE much more than 10 times
is obtained. In reality, other factors are added together, and in one prototype example HFE (25°C)'=;1.79X107HFE (10
0°C) #1.84X10' was obtained.

What should be noted here is that HFE decreases as the temperature increases. This is because in HFEO, the factor expressed by the relational expression +1) has a large influence, and this factor decreases significantly as the temperature rises. This property is a tendency not found in conventional transistors, and is characterized by being less prone to thermal runaway.

FIG. 2 shows an example in which the transistor is applied to an optical coupler type power transistor, where Tr is a transistor having the 5i-Ge-5i structure of the present invention, and a PIN photodiode FD is connected to the base and collector. In the above prototype example, when a base current of 80 μA was applied, a collector current of 55 A could be applied even at 100° C.

In this way, 80 μA is a value that can be sufficiently passed even in an optical coupler type, and in combination with a PIN diode, an ultra-high-speed optical coupler type power transistor can be realized, and together with the isolation effect, the added value can be dramatically increased.

FIG. 3 shows an example of a process for a transistor according to the present invention. A Nu Si wafer is used (first step), and Ge is grown thereon by MOCVD (second step).

Next, a P-type impurity is diffused into this (third step). Furthermore, Si is grown by MOCVD method (fourth step),
°N-type impurity is diffused (fifth step). Finally, the affinities of O Si and Ge, which are etched to form the emitter, base, and collector electrodes (sixth step), are as follows:
There is no need to worry about deterioration.

In this embodiment, the explanation has been made using an NPN) transistor, but P
The same applies to NP) transistors. Moreover, the application example is not limited to optical coupler type power transistors, but the features of the present invention can be applied to any device.

<Effects> As described above, according to the present invention, a useful transistor with high HFE can be provided.

[Brief explanation of the drawing]

Fig. 1 is a Fermi level diagram of a transistor showing an embodiment of the present invention, Fig. 2 is an electrical circuit diagram of an optical coupler type power transistor showing an application example, and Fig. 3 is a process diagram showing an example of the process. . E...emitter section, C...collector section, B...base section. Agent Patent attorney Aihiko Fukushi (and 2 others) 8 (to 1-
) Fig. 1-PfJl, z [n Pot Fig. 2

Claims (1)

[Claims] 1. A transistor characterized in that an emitter part and a collector part are made of silicon (Si), and a base part is made of germanium (Ge).