JPH02240531A - Photodetector - Google Patents

Abstract

PURPOSE:To detect light of a specific wavelength by providing a specifically constituted semiconductor photodetecting element and a signal processing circuit which computes the difference between the output of a 1st photodetector and the output of a 2nd photodetector. CONSTITUTION:This photodetector is constituted of the semiconductor photodetecting element 1 and the signal processing circuit 2. The detecting element 1 consists of a semiconductor substrate 3 of a 1st conduction type (for example, n type) and the 1st photodetector PD 1 is formed in the surface layer part thereof. The 2nd photodetector PD 2 is formed in the other surface layer part. The photodetector PD 1 is formed of an impurity region 4 of a 2nd conduction type (for example, p type). The photodetector PD 2 has an impurity region 5 of a 2nd conduction type formed similarly with the impurity region 4 of the photodetector PD 1. An impurity region 6 of the 1st conduction type of a high concn. is so formed as to cover this impurity region 5. Different outputs are generated in the respective photodetector when the photodetector PD 1, PD 2 are irradiated with the same light. The difference between these outputs calculated by the signal processing circuit 2 is proportional to the light component of the specific wavelength region in the light to be detected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a photodetection device that detects light in a specific wavelength band using a semiconductor element.

[Conventional technology]

Conventionally, in order to detect light in a specific wavelength band, an optical filter is generally placed in front of an optical sensor, and the characteristics of this optical filter are adjusted according to the wavelength band of the light to be detected. , a light component having a specific wavelength band, for example, a light component having a specific wavelength band from red to infrared light, is detected from the detected light.

Alternatively, light in a specific wavelength band has been detected by placing a spectrometer such as a prism in front of the optical sensor.

[Problem to be solved by the invention]

However, detection of light in a specific wavelength band using the conventional configuration described above has the problem of high costs because the front filter and spectrometer are expensive, and these optical filters and spectrometers also absorb moisture. As a result, there was a problem that the transmittance decreased and the reliability deteriorated over time.

[Means to solve the problem]

The present invention has been made to solve these problems, and includes a first light receiving section in which a second conductivity type impurity region is formed in a first conductivity type semiconductor substrate and a second conductivity type impurity region formed in the first conductivity type semiconductor substrate. a semiconductor photodetector element having a second light receiving section formed therein and a highly concentrated impurity region of the first conductivity type formed in the lower layer thereof; and a signal processing circuit that calculates a difference in output of each light receiving section. It is something that

[Effect]

When the same light is irradiated to each of the first and second light receiving sections, different outputs are generated in each light receiving section, and the difference between these outputs calculated by the signal processing circuit is determined by the specific wavelength of the detected light. It becomes proportional to the light component of the band.

〔Example〕

FIG. 1 is a conceptual diagram showing an embodiment of the present invention, in which light components in a specific wavelength band from red to infrared are selected and detected.

The photodetection device is composed of a semiconductor photodetection element 1 and a signal processing circuit 2.

The semiconductor photodetector element 1 consists of a semiconductor substrate 3 of a first conductivity type (for example, p-type), and a first light-receiving section PDI is provided on the surface layer thereof.
is formed, and a second light receiving portion PD2 is formed in the other surface layer portion. The first light receiving portion PD1 is formed from a second conductive 7m type (for example, p type) impurity region 4. The second light receiving portion PD2 has a second conductivity type impurity region 5 formed similarly to the impurity region 4 of the first light receiving portion PDI. An impurity region 6 is formed.

Further, the semiconductor substrate 3 of the first conductivity type is connected to an external terminal X via an electrode not shown, and each impurity region 4.5 of the second conductivity type is connected to terminals y and z similarly via an electrode not shown. has been done. Each of these terminals is connected to a signal processing circuit 2, and the signal processing circuit 2 calculates the difference between the output of the first light receiving section PDI and the output of the second light receiving section PD2.

The semiconductor photodetector element 1 is formed, for example, as follows.

In other words, the semiconductor substrate 3 is silicon (S) containing phosphorus (P).
i) is formed into an n-type as a material, and the first light receiving part PCI
The impurity region 4 contains boron (B) in the surface layer of the semiconductor substrate 3.
is selectively diffused to form a p-type. This p
type impurity region 4 forms a pn junction with p-type semiconductor substrate 3. Further, the impurity region 5 of the second light receiving portion PD2
boron is selectively diffused to form a p-type impurity region 4 having the same shape and the same concentration as the impurity region 4 of the first light receiving part PCI, and an n-type impurity region 6 containing a high concentration of phosphorus so as to cover this impurity region 5. is formed.

P-type impurity region 5 and n-type impurity region 6 form a pn junction. In the manufacturing process, this impurity region 6 is first formed, and after this manufacturing process, the impurity region 5 and the impurity region 4 of the first light receiving portion PDI are formed in the same manufacturing process.

Further, the photodetection characteristics of each of the light receiving portions PDI and PD2 of the semiconductor photodetection element 1 formed as described above are shown in the graph of FIG. In addition, the horizontal axis of the same figure is the wavelength of light [nm],
The vertical axis represents sensitivity.

The first light receiving section PDI has a characteristic shown by a characteristic curve 7, and detects a light component including a short wavelength band of ultraviolet light to a long wavelength band of infrared light. The second light receiving portion PD2 has the characteristics shown in characteristic curve 8, and does not include the long wavelength band from red to infrared,
Detects light components in the short wavelength band from ultraviolet light to visible light. Furthermore, each of the characteristic curves 7.8 has the same characteristics in the short wavelength band, and this is because the impurity regions 4.5 of each of the light receiving sections PDI and PD2 are formed in the same manner.

In such a configuration, when the semiconductor photodetecting element 1 is irradiated with detected light including red to infrared light, carriers are generated in the p-type semiconductor substrate 3.

Generally, light components with short wavelengths do not reach deep positions in the substrate and generate carriers in shallow positions, and light components with long wavelengths generate carriers in deep positions of the substrate. Also, the first
The depletion layer in the second light receiving portion PDI does not appear at a shallow position near the surface, and the depletion layer in the second light receiving portion PD2 is located in the lower layer of the impurity region 5 n! Since the impurity region 6 of a is present, it is formed at a shallow position. Furthermore, the range where carriers are captured in the depletion layer (within the carrier diffusion distance) is within the first light receiving portion PD.
I is located at a deep position of the substrate, and the second light receiving portion PD2 is located at a shallow position of the substrate. Therefore, the first light receiving part PDI
detects carriers generated by optical components in the short wavelength band to long wavelength band, and the second light receiving section PD2 detects carriers generated by optical components in the short wavelength band. Therefore, the detected light is converted into a current for each light component, and the first
The light component detected by the second light receiving portion PD2 becomes a current IA flowing from the n-type semiconductor substrate 3 to the p-type impurity region 4, and the light component detected by the second light receiving portion PD2 becomes n
A current 18 flows from the + type impurity region 6 to the p type impurity region 5.

The detected currents 1 and l are taken into the signal processing circuit 2 via the terminals y and z, and are returned to the semiconductor substrate 3 via the terminal X. Then, in the signal processing circuit 2, a difference current between each current 1 and l is calculated. The value of this difference current is determined to a predetermined value depending on how the impurity region 6 of the second light receiving portion PD2 is formed, and corresponds to a light component having a specific wavelength band of red to infrared light. That is, the current IA follows the characteristic curve 7 shown in FIG.
The current IB is proportional to the sensitivity of the characteristic curve 8. Therefore, the signal processing circuit 2
The difference current obtained by subtraction is proportional to the sensitivity of the characteristic curve 9 shown by the thick solid line in the figure, and only light having light components in the red to infrared wavelength band is detected. becomes possible.

Therefore, according to the above embodiment, it is possible to detect light components in the red to infrared region of a specific wavelength band without using conventional expensive and unreliable optical filters and spectrometers. Furthermore, since the device is constructed of the semiconductor photodetector element 1 with a simple structure and the signal processing circuit 2 with a simple structure, it can be easily provided at low cost and with high reliability.

In addition, in the above embodiment, the first conductivity type is n type,
Although the case where the second conductivity type is p type has been described, there is no need to be limited to this, and the first conductivity type may be p type and the second conductivity type may be n type, and the same effects as in the above embodiments can be achieved. .

〔Effect of the invention〕

As described above, the present invention provides a first light receiving section in which an impurity region of a second conductivity type is formed in a semiconductor substrate of a first conductivity type, and an impurity region of a second conductivity type is formed in a lower layer of the first light receiving section. By using a semiconductor photodetecting element having a second light-receiving section in which an impurity region of the first conductivity type is formed, and a signal processing circuit that calculates the difference between the outputs of each light-receiving section, When the same light is irradiated to each of the light receiving sections in 2, different outputs are generated at each light receiving section, and the difference between these outputs calculated by the signal processing circuit is determined by the light component in a specific wavelength band of the detected light. It becomes proportional.

Therefore, there is no need for conventional expensive and unreliable optical filters and spectrometers, and it is possible to detect light of a specific wavelength using an inexpensive and reliable device.

Impurity region of second conductivity type (p type), 6... High concentration impurity region of first conductivity type.

Patent applicant Hamamatsu Photonics Co., Ltd. Representative Patent Attorney
Yoshikima Shio for Hase
1) Tatsuya

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram showing an embodiment of the device according to the present invention, and FIG. 2 is a graph showing the light detection characteristics of the device shown in FIG. 1... Semiconductor photodetector element, 2... Signal processing circuit, 3
...First conductivity type (n type) semiconductor substrate, 4.5...
light! g! Construction cost procedure amendment form

Claims (1)

[Claims] a first light-receiving section in which an impurity region of a second conductivity type is formed in a surface layer portion of a semiconductor substrate of a first conductivity type; a semiconductor photodetector element having a second light receiving section in which a highly concentrated first conductivity type impurity region is formed below a conductivity type impurity region; and an output of the first light receiving section and the second light receiving section; A photodetecting device comprising a signal processing circuit that calculates a difference between the output of the