JPH0274079A - Photodiode - Google Patents

Abstract

PURPOSE:To enable a photodiode of this design to be effective against a long wave band, operable at a zero bias, and excellent in mechanical strength by a method wherein an impurity level is formed inside a depletion layer forbidden band of a junction. CONSTITUTION:A P region 103 doped with boron through an ion implantation method is formed in an N-Si substrate 104 doped with phosphorus as a dopant, a Au diffused region is formed through a thermodiffusion method, and lead-out electrodes 101 and 105 are formed after a SiO2 protective film 102 has been formed through a wet type thermal oxidation method. As Au forms a deep impurity level inside a Si forbidden band, a light absorption concerned with an impurity level occurs, so that a photodiode grows sensitive to light rays whose wavelength is corresponding to this level. By this setup, the photodiode is made to be effective even against a long wave band, operable at a zero bias, and excellent in mechanical strength.

Description

[Detailed description of the invention] [Industrial application fields] The present invention relates to a photodiode that is effective in long wavelength bands.

[Prior Art] Conventionally, as a photodetector in a long wavelength band, a P-N junction photodiode using a semiconductor material having a narrow bandgap such as nAs, or a PbS photodiode has been used.

[Problem to be solved by the invention] However, the conventionally used
N-junction photodiodes have problems such as the need to use expensive materials and their inability to be used at wavelengths of 2 μm or more.

In addition, since photoconductive elements require a bias voltage to obtain an optical signal, a photocurrent is detected even when there is no optical signal, so-called dark current flows, so they are not suitable for detecting minute amounts of light. .

In addition, since a calorimeter is an assembly of extremely thin thermocouples, its mechanical strength is weak (and high-speed measurement is impossible because the signal output is delayed by several 100 ms with respect to the optical input to measure calorific value).

Therefore, the present invention solves these conventional problems and is effective even in the long wave band. The aim is to obtain a photodetector element that operates with zero bias and is mechanically strong.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the photodiode of the present invention is a photodiode having a PM junction or a PIN junction, in which a forbidden impurity level is created in the depletion layer region of the junction. It is characterized by the fact that it has been formed.

[Example] An example of the present invention will be described below with reference to the drawings. Fig. 1 is a sectional view of a photodiode of the present invention.
〆In Figure 1,
N-S i substrate 104 using phosphorus as a dopant
P region 1 doped with boron by ion implantation method
03, an Au diffusion region 106 was formed by a thermal diffusion method, a 5102 protection@102 was formed by a wet thermal oxidation method, and then the drawers 101 and 105 were directly formed.

Since Au forms deep impurity levels (0,55ev and (L54eV) in the S1 forbidden band, light absorption related to the impurity levels occurs, and it is sensitive to wavelengths corresponding to these two levels. It becomes like this.

Therefore, the spectral sensitivity characteristic has a bimodal wide wavelength sensitivity range as shown in FIG. 2, making it an effective detection device even in the long wavelength range.

In addition, in terms of absolute sensitivity characteristics, the wavelength is 2.1μ77 compared to a normal calorimeter-type thermocouple photometer! about 100 in
IiK, which has 0 times the sensitivity and uses a calorimeter-type thermocouple light meter, does not require the ultra-precision electronic circuit that was considered essential, and can be used with a single general-purpose operational amplifier.

Furthermore, the response time to optical input is within 20 μs at zero bias, making it an extremely high-speed operation for a photodetector in the long wavelength range.

In addition, especially when high-speed operation (5 μs) is required, applying a reverse bias voltage is an effective means, so the photodiode shown in Figure 1 can be used in a measurement system as shown in Figure 3. It was measured by

In FIG. 3, since the inverting input terminal of the operational amplifier 505 is virtually grounded, a reverse bias of ICIV is applied to the photodiode 305. Also, the return resistor 304 is I
KΩ was used.

Further, a semiconductor laser 502 was used as a light source, and pulsed driving was performed by a drive circuit 501. This drive circuit 301
The pulse rise time of is less than 5n3 in 10%-90%.

When examining the rise time of the photodiode 303 using such a circuit system, the rise time of 10%-90% is 4.5.
It was μs.

When used with a reverse bias of 1, a generation-recombination current flows from the PN junction, so it is preferable to operate at a low temperature, but this is especially necessary when dealing with strong light such as laser light. Not that.

In this example, a PM junction photodiode using Sl was explained, but of course this also applies to compound semiconductors such as GaAs, nP, Zn5e, and 0dTa, their mixed crystals, superlattices, and superlattices containing mixed crystals. It is also possible to use group Ⅰ materials such as Ge and 5iGe together with the compound semiconductor.

In addition, dopants are not limited to gold, but also Or, Fe, sb, and P.
Of course, metals and metalloids such as A, Ml, Ag, Ll, and O may be used, and one may be selected according to the desired spectral sensitivity.

Further, the structure is not limited to a planar PN junction, and a PIN junction or a heterojunction may of course be used, and the dopant is not limited to a single type, but several types may be used at the same time.

Furthermore, when a photodiode is used, it normally operates satisfactorily at room temperature, but when the input light intensity is extremely low in a long wavelength band of 5 μm or more, it is better to use it by cooling it to reduce noise.

[Effects of the Invention] The photodiode of the present invention has the following effects.

(IJ) Since a semiconductor doped with deep levels is used, it will not be affected by small amounts of impurities, so it can be used even with low-quality crystal materials, and even if there is a slight distortion in the manufacturing process, the characteristics will be almost constant. (11) Since the device generates photovoltaic force, the dark current is 0 during zero bias operation, and unlike photoconductive devices, the dark current fluctuates due to temperature changes. Furthermore, since dark current does not occur even when the element changes over time, it is possible to detect very small amounts of light.

(1u) Since the sensitivity is about 1000 times higher than that of a calorimeter-type thermocouple photometer, electrical processing of signal output is facilitated.

It is also mechanically extremely strong and will not be damaged by vibrations.

Moreover, it can be extremely miniaturized, and light in a minute area can be detected with high precision.

(1■) The electrical response speed to optical input is extremely fast, about 10 μs at zero bias, and fields that require high speed (
It can also be applied to optical output control of laser beams, etc.).

By changing the M doping material, the spectral sensitivity characteristics can be greatly changed, and an operating region beyond the long wavelength limit resulting from the limitations of semiconductor materials can be utilized, which is effective in designing optical ICs and the like.

In addition, it is possible to easily make an optical detector that can be used in a wavelength range of about 5 μm using Sl, and if a slight decrease in sensitivity is acceptable, a photodetector that can be used in a wavelength range of up to @10 μm can be obtained. A long-wavelength detector can be constructed from inexpensive silicon without using other materials.

(It has a P-1J structure, and by applying a reverse bias, the electrical response speed to optical input can be improved to about 2fLS, and it can be applied to information fields that require ultra-high-speed response.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a photodetecting element for explaining the present invention in detail. FIG. 2 is a spectral sensitivity characteristic diagram for explaining the present invention in detail. FIG. 3 is a circuit diagram of a measurement system for explaining the present invention in detail. 101...Extractor electrode 102...SiO□protective film 103...
...P region 104..., ...N-Si substrate 105...
...Extraction electrode 106...Au diffusion region 601...
...Drive circuit 302...Semiconductor laser 303...
...Photodiode 304...
Feedback resistor 305・・・・・・Operational amplifier or higher Applicant Seiko Epson Co., Ltd. Agent Patent attorney Masayoshi Ueyanagi (1 other person) Toda], O Yu, Ke 3.0 3, #F

Claims (1)

[Claims] 1. A photodiode having a PN junction or a PIN junction, characterized in that an impurity level is formed in a forbidden band of a depletion layer region of the junction.