JPS5927580A - Photosemiconductor device - Google Patents

Abstract

PURPOSE:To enable to reduce leakage current by interposing an n<-> type A GaAs semiconductor layer between an n<-> type GaAs semiconductor layer and a Schottky electrode. CONSTITUTION:An n<-> type A GaAs semiconductor layer 7 which has, for exmple, a thickness of 1.9(mum) is inserted between an n<-> type GaAs semiconductor layer (light absorption layer) 2 and a Schottky electrode 4. The layer 2 may be converted into n<-> type A GaAs semiconductor layer. The photoreceiving diameter of a photodetector PD is 200(mum), the width of the channel of an FET is 50(mum), the length of a gate is 2(mum), the distances between source, drain an gate, drain are 3(mum), and the insulation between the photodetector PD and an amplifier AMP is performed by semi-insulating GaAs substrate 11 and a groove 18.

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to an optical semiconductor device called a Schottky barrier photodetector suitable for use, for example, in transmitting optical signals.

Conventional technology and problems Conventionally, for example, when transmitting light with a wavelength in the 0.8 [μm] band, a photodetector with the structure shown in Figure 1 is used to detect light. I know ζ.

In the figure, l is an n'' type GaΔS semiconductor substrate, 2 is an n-type GaΔS semiconductor layer with a thickness of, for example, about 5 μm, and 3
is a silicon dioxide (Si02) insulating film, 4 is a Schottky electrode made of platinum (PL) with a thickness of, for example, 200 μm, 5 is an electrode made of gold (ΔU) with a thickness of, for example, 3000 μm, and 6 is an electrode made of gold. f[i
4Igi are shown respectively.

In this photodetector, the arrow in the figure indicates lFt.)
Light enters through the Schottky electrode 4, and carriers are generated in the semiconductor 1'tiZ to the n-type Ga8, and the carriers are taken out from the electrode 5 and become an external current.

FIG. 2 is a circuit diagram for explaining an example of a circuit configuration when using the photodetector of FIG. 1.

In the figure, l) D is a photodetector, PS is a bias power supply, Rpd is a load resistance, 0'1' is an output voltage, and hv is an incident light.

By the way, this conventional example has a drawback that the leakage current of the Schottky barrier is large, and if the leakage current is large,
It is not practical unless the 1fi current increases and the optical power of the incident light is large. This tendency becomes noticeable when the bias voltage (2) is large.

OBJECTS OF THE INVENTION The present invention provides a Schottky barrier photodetector with reduced leakage current.

Structure of the Invention In the present invention, we take advantage of the fact that the Schottky barrier between AlGaAs and metal has a high barrier height compared to that between GaAs and metal.
A low-type ΔIGaΔS semiconductor layer is interposed between the n-type AlGaAs semiconductor layer (or n-type AlGaAs semiconductor layer) and the cylindrical electrode.
As a result, a photodetector with reduced leakage current can be obtained.6 Embodiment of the Invention FIG. 3 is a cutaway side view of a main part of an embodiment of the present invention, and the explanation with respect to FIG. Parts and parts that are the same are indicated by the same symbol.

The difference between this embodiment and the conventional example shown in FIG. 1 is that the n-type Ga
An n-type to IGa S semiconductor layer 7 having a thickness of, for example, 1.9 μm is inserted between the AS semiconductor layer (light absorption layer) 2 and the Schottky electrode 4. Incidentally, the I]'' type GaΔS semiconductor 1i1't2 may be replaced with a !1-type AlGa8S as a conductive layer and 'ζ' may also be used.

In this embodiment, with this configuration, leakage current can be reduced to almost zero.

The photodetector described in connection with FIG. 3 is a FET and 8. ■Go-
Something will happen. FIG. 4 illustrates this.

There are 13 numbers in Figure 4, and 11 is the surface index of the main surface (100)
Is it? 1'' color-rimmed GaAsJIl&, 12 is a conductor layer to nl' type Ga8S with 1V of 1.9 Cμm), 1
3 has a thickness of 3.8 [μrn] and an impurity concentration of 4×101
4 (cm-g) is an n-type Ga8 semiconductor layer (light absorption 1m), 14 is an ann-type semiconductor layer (light absorption 1m) with a thickness of 1.9 [μm].
- doped high resistance AI O, 3G a O, 7Δ5-31 conductor layer, 15 is undoped Ga 8sgF, h% J body IFi
, 16 has a thickness of ().

2 [μm] and the impurity concentration is I
+n-3) and is the channel layer of the FET.
aAs semiconductor layer, 17 is a silicon dioxide insulating film, 18 is a groove for connecting the photodetector and amplifier to the insulating film, 19 and 20 are source and drain electrodes made of Ge to ΔU/8u; Aluminum (A1) gate electrode, 22 is a Schottky electrode made of Au with a thickness of 200 mm, 23 is an electrode made of 8 liters with a thickness of 2000 mm, and 24 is an A u G electrode with a thickness of 3000 mm. e
/Ni electrode, PD is a photodetector, and AMP is an amplifier (FET).

The light receiving diameter of the photodetector PD in this device is 200 (717
m), 'The channel width of the FET is 50 (μm), the gate length is 2 [μm], the distances between the source and gate and between the gate and drain are each 3 [μm], and the photodetector PD and A semi-insulating GaAs crystal plate 1 is used to insulate the amplifier from the MP.
1 and groove 18 is also a major feature.

FIG. 5 shows a circuit diagram of the fourth and first apparatus in use, and the same parts as those explained in connection with FIG. 4 are indicated by the same symbols.

In the figure, Rpd is the load resistance of photodetector PD, Rfe
L is the load resistance of MP to the amplifier, Vpd is the photodetector P l
The voltage L applied to -1 [-1V d s is the amplifier ΔM
+) and O'I'' respectively indicate the output voltage.

In this circuit, when light is incident on the photodetector PD, which is non-conducting at points 1 and 2, the photodetector PD becomes conductive and a current flows.

A voltage drop caused by the current flowing through the resistor Rpd is applied to the gate of M+> to the amplifier, and MP is made conductive to the amplifier, so that an output can be obtained from the output &iAl terminal 0'F.

In this device, when we measured the current-voltage characteristics of the photodetector 1) 1), we found that it was a punch-through dark current.
llXl0-10 (8) was added. Also, the amplifier A
When we measured the static characteristics of MP, we found that the pinch-off voltage was 2.
0 (V), 9. ,,=1.7. (ms) is obtained
Renoko.

FIG. 6 is a diagram showing the data obtained by measuring the input/output characteristics of the saw device explained in connection with FIG. 4.

This is a light emitting diode (, LED
), RPd=10(KΩ) + Rf e t
= 10 [KΩ], vpa = o (V), and shows the characteristics of 7 f thick, and the increment of photocurrent is plotted as a function of LED current.

The intensity range of the light used in this experiment (<50 [μ
W)), the current △■pd flowing to the photodetector PD and the current I' ds flowing to the amplifier AMP are proportional to the input light intensity, and a current multiplication factor of 19 can be obtained from the ratio of these. This (yesterday, from 91,1・Rpd・△lpd to rlH
Since it matches the value (dashed line), it can be seen that a crystalline current multiplication characteristic was obtained using the wooden device.

i; In both of the explanations in Section I, low type G'aΔS was used as the semiconductor layer which is the light absorption layer, but this was replaced by nmΔIG
aΔS can also be used. However, in that case, the wavelength of light that can be detected becomes shorter. In addition, by maximizing the composition of 81 at the top of the n-type ΔIGa 8S hemisphere layer on the barrier side, light absorption at this bottom can be avoided (wind layer), and furthermore,
Since the height of the barrier becomes high, it is also effective in reducing leakage current, and there is no concern regarding light transmittance.

Effects of the Invention According to the present invention, G with a low carry concentration as a light absorption layer
To a8 (or AlGa8S) A low-temperature layer with a higher A1 composition ratio than this is placed on the conductor layer lr4 degrees Δl Ga
A photodetector having a structure in which an S44 conductor layer is formed and a silicate electrode through which light is incident is formed on the photodetector is obtained, and this photodetector is obtained by providing the AlGaΔS semiconductor layer with a low carrier concentration. , the leakage current is extremely reduced.

[Brief explanation of the drawing]

Figure 1 is a side view of the main part of the conventional example, and Figure 2 is the 111i side view of the conventional example.
121 in the state of use of the conventional example] I'8
Figure 3 is a cross-sectional side view of the main part of one embodiment of the present invention, and Figure 4 is
The figure shows one embodiment of the present invention explained with reference to FIG.
Figure 5 is a 1/8th view of the device in use as shown in Figure 4. Line 1 represents the input/output characteristics of the device described. In the figure, °C, l is n" type GaΔS semiconductor substrate, 2 is +
]-type Ga 8 to semiconductor gin 3 is silicon dioxide (Si0
2) Insulating film, 4 is silicon/I raw electrode, 5 and 6 are electrodes, 7 is 11-type 1GaΔS semiconductor layer, 11 is semi-insulating G, aΔS substrate, 12 is n1 type QaΔS semiconductor layer, 13
is an n-type Ga8 semiconductor layer, 14 is an undoped high-resistance layer, 15 is an undoped S semiconductor layer, and 16 is an n-type GaA's semiconductor layer. , 17 is a silicon dioxide insulating film, 18 is a groove, 19 and 20 are source and drain electrodes, -21 is a gate electrode, 22 is a silicon dioxide insulating film 23 and 24 are electrodes, P
D is a photodetector and ΔMP is an amplifier. Patent Applicant: Director of National Institute of Industrial Science and Technology Lu Hanwei No. 3 Figure 4 Figure 5 Figure 6 Figure 6 11*d (mA)

Claims (1)

[Claims] A GaAs (or LiAIGaAs) semiconductor layer with a low carry concentration that absorbs light;
lGaAs> A low carrier concentration AlGaAs semiconductor layer having a higher A1 composition ratio than that formed on the semiconductor layer, and a Schottky electrode formed on the low carrier concentration Δ1GaAs semiconductor layer and into which light is incident. Optical semiconductor device.