JPH0621566A - Extremely low current transmission type semiconductor element and semiconductor laser using the same - Google Patents

Abstract

PURPOSE:To provide a semiconductor element wherein the current transmission ratio of a current blocking layer or the like of a semiconductor laser is very low. CONSTITUTION:In a semiconductor element having an N-P type semiconductor layer (emitter) 1, a P-InP type semiconductor layers (base) 2, 4, and an N-InP type semiconductor layer (collector) 5, a P-InGaAsP layer 3 whose energy gap is small is formed between the P-InP semiconductor layers (base) 2 and 4, and operates as a trapping layer for minority carriers injected from the N-InP type semiconductor layer (emitter) 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an extremely low current transmission type semiconductor device and a structure of a semiconductor laser using the same.

[0002]

2. Description of the Related Art Conventionally, as a transistor of this type,
"Electronics Engineering" by Shoji Aoki, Publisher Corona Publishing Co., p. 335-p. 338 were disclosed. FIG. 5 is an energy band diagram of a conventional PNP junction transistor in a thermal equilibrium state, and FIG. 6 is a conventional PNP.
It is an energy band diagram in the state where the bias was added in the operating state of the junction transistor.

In FIG. 5, the emitter, the base and the collector are shown in order from the left, the filling band, the energy gap and the conduction band are shown in order from the bottom, and the dotted line shows the Fermi level. In FIG. 6, a forward bias is applied between the emitter and the base, and a reverse bias is applied between the base and the collector.

The movement of the carrier in this case will be described. First, holes, which are minority carriers, are injected from the emitter junction. The holes diffuse in the base toward the collector, but some of them disappear by recombination. The holes reaching the collector appear as an increase in collector current. The ratio of current I _{E at the} emitter junction to current I _E ^h due to holes flowing from the emitter to the base γ = I _E ^h / I _E is called the emitter efficiency. Of the minority carriers that have flowed into the base, the ratio at which they reach the collector without recombining is called the transport efficiency β, and is expressed as β≈serh (W / Lp). Here, W is the base thickness, and Lp is the diffusion distance of minority carriers (holes in this case) in the base. When the minority carriers reach the collector junction, the collector current usually increases accordingly.

However, a part of the minority carriers reaching the high electric field portion of the collector junction is accelerated by the electric field,
Since there is a probability of creating a new electron-hole pair, the increase I _C of the collector current is slightly larger than the increase I _C ^h due to the minority carriers reaching the collector. This ratio M = I
_C / I _C ^h is called the collector multiplication factor. The product α = γβM of the emitter efficiency γ, the transport efficiency β, and the collector amplification factor M is called a current transfer rate.

FIG. 7 shows an example of a grounded-emitter circuit of a PNP transistor. Current at the rate alpha Tosureba this _{circuit, I C = αI E ...... I} C = I E -I B because ...... holds ,, I _C = from (α / 1-α) I B , and the the closer alpha is sufficient to 1, the circuit of FIG. 7 is a I _B alpha
It can be seen that the current amplification circuit amplifies by 1/1 / α times.

[0007]

However, in the above-mentioned conventional transistor, the performance of the transistor has been improved so that the base is as thin as possible and α is close to 1 from the viewpoint of amplification characteristics and high frequency operation. It was As the base becomes thinner, α inevitably approaches 1.

On the other hand, when a transistor is used as the PNPN current blocking layer, switching and current amplification are not desirable. For α → 0, the base should be made sufficiently thick, or the doping amount of the base should be increased to the extent that the breakdown voltage does not decrease, but if the layer corresponding to the base cannot be made sufficiently thick due to the requirements of the device structure. There is also.
For example, the current blocking layer of a semiconductor laser is the same.

Conventionally, no transistor has been improved in performance (α → 0 in this case) for the purpose of such use. SUMMARY OF THE INVENTION It is an object of the present invention to eliminate the above problems and provide an extremely low current transmission type semiconductor element having a very low current transmission rate such as a current blocking layer of a semiconductor laser and a semiconductor laser using the same.

[0010]

In order to achieve the above object, the present invention provides a first conductivity type first semiconductor layer (1) and a second conductivity type second semiconductor layer (2, 4). A semiconductor element having a third semiconductor layer (5) of the first conductivity type, energy smaller than that of the second semiconductor layer (2, 4) between the second semiconductor layers (2, 4) of the second conductivity type. The fourth semiconductor layer (3) of the second conductivity type having a gap is sandwiched.

In the semiconductor laser, the first conductivity type first semiconductor layer (11), the second conductivity type second semiconductor layer (12), and the first conductivity type third semiconductor layer (14) are used. A second laser having an energy gap smaller than that of the second semiconductor layer (12) between the second semiconductor layers (12) of the second conductivity type.
The conductive fourth semiconductor layer (13) is sandwiched therebetween.

[0012]

According to the present invention, as described above, the first conductive type first semiconductor layer (emitter) 1, the second conductive type second semiconductor layers (base) 2 and 4, and the first conductive type A semiconductor element having a third semiconductor layer (collector) 5 of
The second semiconductor layer (base) 2 and 4 of conductivity type
The fourth semiconductor layer 3 of the second conductivity type having a smaller energy gap than the semiconductor layers (bases) 2 and 4 is sandwiched.

Therefore, the second conductivity type fourth semiconductor layer 3 having a small energy gap acts as a trap layer for the minority carriers injected from the first conductivity type first semiconductor layer (emitter) 1, and the current transmission. The rate can be very low. Further, the current confinement can be improved by using it for the current blocking layer of the semiconductor laser.

[0014]

Embodiments of the present invention will be described in detail below with reference to the drawings. 1 is a structural diagram of a semiconductor element (transistor) showing an embodiment of the present invention, and FIG. 2 is an operation explanatory diagram of a semiconductor element (transistor) showing an embodiment of the present invention. Here, an InP / NPN type bipolar semiconductor element (transistor) will be described as an example.

In the figure, 1 is an n-InP type semiconductor layer as a first semiconductor layer (emitter) of the first conductivity type, and 2, 4
Is p-I as the second semiconductor layer (base) of the second conductivity type.
nP type semiconductor layer, 3 is a p-InGaAsP trap layer that is a fourth semiconductor layer of the second conductivity type, and 5 is a third layer of the first conductivity type.
It is an n-InP type semiconductor layer as a semiconductor layer (collector).

As shown in this figure, between the p-InP type semiconductor layer (base) 2 and the p-InP type semiconductor layer (base) 4, there is a small energy gap with respect to the mean free path of minority carriers. The thick p-type semiconductor layer 3 is sandwiched. For example, InGaAsP corresponds to InP. This is an n-InP type semiconductor layer (emitter)
Since it acts as a trap layer for the minority carriers injected from, the transport efficiency α _T becomes very low, as shown in FIG. Since the current transfer rate α of this semiconductor element (transistor) is represented by the product α _E · α _T · α _C of the injection efficiency α _E of the minority carrier, the transport efficiency α _T , and the collector efficiency α _C ,
The transmission efficiency of this semiconductor element (transistor) is almost zero.

In FIG. 2, p-InP layer (base)
2,4 valence band and p-InGaAsP trap layer 3
The energy gap between the lower end is In_XGa_1-xA
s_YP _1-Y, It changes according to the values of x and y,
For example, it can be reduced to 0.75 eV to 1.3 eV.
Wear. Incidentally, the p-InGaAsP trap layer 3 is provided.
In the absence of the energy gap is 1.34 eV.

FIG. 3 is a sectional view of a semiconductor laser having a PNPN thyristor current block layer (base layer of an NPN transistor) according to the present invention, FIG. 4 is an equivalent circuit of the semiconductor laser, and FIG. FIG. 4B is a diagram showing the relationship between the laser structure and its equivalent circuit, and FIG. 4B is a diagram showing only its equivalent circuit. In FIG. 3, 11 is an n-InP substrate as the first semiconductor layer of the first conductivity type, and 12 is a second semiconductor layer.
A p-InP block layer as a conductive type second semiconductor layer,
Reference numeral 13 denotes a p-InGaAsP trap layer as a fourth semiconductor layer of the second conductivity type having a small energy gap, 14 is an n-InP block layer as a third semiconductor layer of the first conductivity type, and 15 is an n-InP clad layer. 16 is InGaAs
P active layer, 17 is p-InP clad layer, 18 is p-I
nGaAsP contact layer, 19 is AuGeNi and Au
And a laminated electrode 20 and an AuZn electrode 20.

Here, the extremely low current transmission type semiconductor element (transistor) of the present invention is used as a current block layer of a semiconductor laser. Then, the leakage current is I _l = α ₂ I _G + I
_{CO / 1-α 1 -α 2} (I CO is the reverse current of the portion hazy reverse voltage, α _1, α ₂ is the current transmission efficiency of each transistor) since the, α _1, α ₂ → 0 Therefore, I _l =
It becomes I _CO .

Therefore, the leak current can be made extremely small, and the current confinement of the semiconductor laser can be improved. In FIG. 4, 30 is a current block circuit including a PNP type transistor 31 and an NPN type transistor 32, and r _{1 to} r ₅ are equivalent resistors. Also in this embodiment, in the second conductivity type fourth semiconductor layer having a small energy gap, the energy gap is
Similar to the embodiment, it can be reduced to 0.75 eV to 1.3 eV, for example.

The present invention is not limited to the above-mentioned embodiments, but various modifications can be made within the scope of the present invention, and these modifications are not excluded from the scope of the present invention.

[0022]

As described in detail above, according to the present invention, a semiconductor having the same conductivity type as the base layer having a smaller energy gap than the base layer is sandwiched, so that the current transfer rate is extremely high. It is possible to obtain an extremely low current transmission type semiconductor device and a semiconductor laser using the same.

[Brief description of drawings]

FIG. 1 is a structural diagram of a semiconductor element (transistor) showing an embodiment of the present invention.

FIG. 2 is an operation explanatory diagram of a semiconductor element (transistor) showing an embodiment of the present invention.

FIG. 3 is a cross-sectional view of a semiconductor laser having a PNPN thyristor current block layer (base layer of NPN transistor) according to the present invention.

FIG. 4 is an equivalent circuit of the semiconductor laser of FIG.

FIG. 5 is an energy band diagram in a thermal equilibrium state of a conventional PNP junction transistor.

FIG. 6 is an energy band diagram in a state where a bias is applied in the operating state of the conventional PNP junction type transistor.

FIG. 7 is a grounded-emitter circuit diagram of a conventional PNP transistor.

[Explanation of symbols]

 1 n-InP type semiconductor layer (emitter) 2,4 p-InP type semiconductor layer (base) 3 p-InGaAsP trap layer 5 n-InP type semiconductor layer (collector) 11 n-InP substrate 12 p-InP block layer 13 p-InGaAsP trap layer 14 n-InP block layer 15 n-InP clad layer 16 InGaAsP active layer 17 p-InP clad layer 18 p-InGaAsP contact layer 19 AuGeNi / Au electrode 20 AuZn electrode

Claims (6)

[Claims] 1. A semiconductor device having a first conductive type first semiconductor layer, a second conductive type second semiconductor layer, and a first conductive type third semiconductor layer, wherein the second conductive type second semiconductor layer is used. A fourth conductive type having a smaller energy gap between the semiconductor layers than the second semiconductor layer;
An extremely low current transmission type semiconductor device having a structure in which a semiconductor layer is sandwiched. 2. The first semiconductor layer of the first conductivity type is n-I
The emitter of the nP layer, the second semiconductor layer of the second conductivity type is p
-The base of the InP layer and the third semiconductor layer of the first conductivity type are n-
The fourth semiconductor layer of the second conductivity type, which is a collector of the InP layer and has a small energy gap, is p-InGaAs.
The extremely low current transmission type semiconductor device according to claim 1, which is a P trap layer. 3. The small energy gap is 0.7
The extremely low current transmission type semiconductor device according to claim 2, which has a voltage of 5 eV to 1.3 eV. 4. A semiconductor laser having a current blocking layer including a first-conductivity-type first semiconductor layer, a second-conductivity-type second semiconductor layer, and a first-conductivity-type third semiconductor layer. A fourth conductive type fourth semiconductor having an energy gap smaller than that of the second conductive semiconductor layer between the second conductive semiconductor layers.
A semiconductor laser having a structure in which a semiconductor layer is sandwiched. 5. The first semiconductor layer of the first conductivity type is n−I.
nP layer substrate, the second conductive type second semiconductor layer is p-In
The P block layer and the third semiconductor layer of the first conductivity type are n-InP
5. The semiconductor laser according to claim 4, wherein the block layer and the fourth semiconductor layer of the second conductivity type having a small energy gap are p-InGaAsP trap layers. 6. The small energy gap is 0.7
The semiconductor laser according to claim 5, which has a voltage of 5 eV to 1.3 eV.