JPS6364370A - Semiconductor phoetodtector - Google Patents

Abstract

PURPOSE:To vary equivalent beam/current conversion efficiency by controlling a depletion layer formed near a first layer as an optical absorption layer by external applied voltage and controlling the quantity of currents bypassing to the substrate side of a P-I-N photodiode. CONSTITUTION:A semiconductor photodetector has a beam/current conversion function by a P-l-N photodiode constituted of semiconductor layers 3-5 and a function controlling the quantity of inflow to a substrate 1 of currents beam/ current converted by the P-I-N photodiode by controlling a depletion layer 10 shaped into the layer 4 by the application of a reverse bias to a P-N junction organized of semiconductor layers 1', 2, 4 by applied voltage. Beams projected from the semiconductor layer 5 side are absorbed into the semioonductor layer 4, and holes and electrons are generated. These holes and electrons are drifted by an electric field in the layer 4, and electrons flow into the substrate 1 and the semiconductor layers 3 and holes into the semiconductor layer 5, and currents of I1=I2+I3 flow. With this element, the region of the depletion layer 10 can be controlled by controlling V2, and the current value of I2 used as light-receiving signal currents can be controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor light-receiving element used in optical communication using an original fiber.

[Conventional technology]

In conventionally used PIN photodiodes, there is a very large difference in the output current between the small and large PIN photodiodes. Normally, this output difference is dealt with by making the amplification factor of the amplifier circuit connected after the PIN variable.

[Problem that the invention seeks to solve]

However, the variable range of the gain of the amplifier circuit needs to be 60 dB, and the configuration of the electric circuit becomes complicated.

An object of the present invention is to provide a semiconductor light receiving element, such as a PIN photodiode, whose light/current conversion efficiency can be equivalently controlled by an externally applied voltage. [Means for solving the problems] The present invention has a first semiconductor layer doped with one conductivity type, a second semiconductor layer doped with the other conductivity type, and a third semiconductor layer doped with one conductivity type thereon. The semiconductor has a 1゛Δ of
a fourth doped semiconductor layer;
The other conductivity of impurities and summer =:l IP+4
, Oon-? 4i+'+': rhaM hill;,i
4 sho; F# ii l r'L
+() A part of the semiconductor layer is directly behind the first semiconductor layer.

[Effect]

The present invention controls the depletion layer formed in the fourth layer, which is the light absorption layer, and near the first layer, which is the substrate, by an externally applied voltage, and controls the current flowing through the PIN photodiode toward the substrate side. The most important feature is that the isometric light/current conversion efficiency is made variable by fully controlling the amount of bypassed current.

〔Example〕

FIG. 1 is a diagram for explaining the first embodiment of the present invention, in which 1 is a −(p+) type InP substrate, 11 is an n(p)ffl
InP buffer layer, 2 is p (n) type InP layer, 3 is n
(p) type InGaAsP layer, 4 is n-(p-) type I
nGaAa layer, 5 is a p"(n") type InGaAs layer formed by ion implantation into the InGaAs layer, 6 is layer 5
and ohmic electrode, 7 is plasma CVD method or E
4 S 13N layers for high performance fabricated by CR method, 8 is a reverse bias power supply (V2) for controlling the depletion layer, 19 is a reverse bias power supply for PIN photodiode formed by 3, 4.5 layers (
Vl), 10 is a depletion layer, 11 is a guard ring made by Cd implantation using an ion implantation method in order to completely reduce the electric field strength around the semiconductor layer 5, and 12 is a load resistor for signal detection.

Note that 0 in layers 1, 2 to 5 of the substrate 12 indicates the case where the layers were fabricated on a p-type substrate.

In Figure 1, Engineering 11 Engineering 2pI3 is top notch.

Next, the basic operation of this device will be explained.

The functions of this element can be roughly divided into two functions.

The first function is a light/current conversion function by a PIN photodiode constructed from the semiconductor layer 3,415 in FIG.
The second function is the semiconductor layer 1' in FIG.

The depletion layer 10'f formed in the layer 4 by applying a reverse bias to the PN layer 4 composed of 2.4 is photo/DC converted by the PIN photodiode by controlling the applied voltage. This function controls the amount of current flowing into the substrate 1.

In FIG. 1, light incident on the semiconductor layer 5 is absorbed within the semiconductor layer 4, and all holes and electrons are generated. These holes and electrons are lifted by the electric field in the layer 4, the electrons flow into the substrate 1 and the semiconductor layer 3, the holes flow into the semiconductor layer 5, and a current flows such that s t ='2 + Is .

On the other hand, in this device, by controlling V, the depletion J-1
0 area can be controlled.

Therefore, the size of the crack 3 caused by the electrons flowing into the substrate 1 can be controlled. As a result, the current value of the circuit 2 used as the light reception signal current can be controlled.

Table 1 shows examples of the main structural parameters of wood grains.

〔Effect of the invention〕

As explained above, since the present invention can control the magnitude of the signal current by externally applied voltage, when used as a light receiving circuit for optical fiber communication, the signal current value at the maximum and minimum light receiving power required by the method The ratio of can be reduced. Therefore, the AGC of the amplifier circuit connected after the next stage of the light receiving element
This has the advantage that the required magnitude for automatic gain control (automatic gain control) can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a first embodiment of the invention. 1-n(p) InP substrate, 1'-n(p) type 1nP buffer layer, 2...p(n) type InP layer, 3
-”nφ)W InGaAsP r=,4-=n-(p
-'') type InGaAs layer, 5 = -p (n-) type 1n
GaAs f'3゜6... J connection 5 and ohmic electrode, 7... Si, N4 layer for extremely low density, 8... Reverse bias power supply for depletion layer control, 9... For PIN photodiode Reverse bias power supply, 10... depletion layer, 11... guard ring, 12... load resistance, 0 indicates the case of a p-type substrate.

Claims (1)

[Claims] A first semiconductor layer doped with one conductivity type has a second semiconductor layer doped with the other conductivity type, and a third semiconductor layer doped with one conductivity type is formed on top of the second semiconductor layer doped with the other conductivity type. have,
a fourth semiconductor layer doped with one conductivity type with a low impurity concentration thereon; a fifth semiconductor layer doped with the other conductivity type with a high impurity concentration thereon; A semiconductor light-receiving element, wherein a part of the semiconductor layer is in direct contact with a first semiconductor layer.