JPS6132582A - Light transmission type semiconductor photodetector - Google Patents

Abstract

PURPOSE:To obtain a small-sized device having high optical transmittance and photoelectric conversion efficiency by forming a semiconductor layer, EG thereof is smaller than hnu and impurity concentration therein is lower than a specific value, to a p-n junction section while bringing the transmittance of beams reaching to one main surface from the other main surface to a specific value or more. CONSTITUTION:A photodetecting section in which a semiconductor layer 22, a band gap EG thereof is smaller than the energy hnu of input beams and impurity concentration therein is lower than 1X10<19>cm<-3>, is formed onto a first conduction type semiconductor substrate 21, EG thereof is larger than hnu, and a semiconductor layer 23, EG thereof is larger than hnu and which has a conduction type reverse to the semiconductor substrate 21, is shaped onto the semiconductor layer 22 is constituted. The transmittance of beams reaching to one main surface from the other main surface is brought to 50% or more. The layer 22 such as an In0.25Ga0.75As one 22 in doner concentration of 1X10<15>cm<-3> is grown on the substrate 21 such as an n type GaAs one 21 to which Te is doped, and the layer 23 such as a p type GaAs one 23 to which zinc is doped is grown on the layer 22. Optical transmittance is controlled by the thickness of the optical absorption layer 22.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a semiconductor photodetection device that transmits or reflects light and converts a portion of an input destination into an electrical signal.

[Technical background of the invention and its problems]

Conventional semiconductor photodetectors using semiconductor PN junctions or Schottky junctions absorb light and perform photoelectric conversion, and in order to increase the photoelectric conversion efficiency, the semiconductor layer must be thick enough to absorb the incident light. It is opaque. In order to perform light detection using only a part of the incident light and transmit the other light and output it to the outside, a half mirror 2 is inserted in the optical path of the incident light 1, as shown in FIG. 4, a part of the incident light is reflected, and the reflected light is detected by the photodetector 5. This method requires a space to fix the half mirror and a device to adjust the inclination of the half mirror 2, making it difficult to make the light detection system small. When applied to circuits, etc., it cannot be used. Also, since Hahn Min uses a thin gold RM coating, it has the disadvantage of low transmittance.

Another method is to make the PN junction of the semiconductor a thin film and increase the optical transparency by 4=J, but in this case, there is light absorption in the electrically neutral region of the semiconductor that does not become a depletion layer. This results in a loss of light transmittance.

[Purpose of the invention]

An object of the present invention is to eliminate the above-described drawbacks of the semiconductor photodetection device, and to provide a compact semiconductor photodetection device that has high light transmittance and high photoelectric conversion efficiency.

[Summary of the invention]

Semiconductor photodetector according to the present invention, Bandganon J
,! ! (] is the incident light energy 11ν (h is the blank constant, ν is the original frequency) to form a PN junction using a semiconductor material larger than that, and in the PN reed part Mo is smaller than hν and is an impurity. It is characterized by providing a semiconductor layer having a concentration lower than .

〔Effect of the invention〕

According to this invention, an internal electric field can be applied to the entire semiconductor layer (2) that absorbs light and generates pairs of electrons and holes, so that electrons and holes are reversed by the internal electric field. Therefore, the probability of recombination of electrons and holes is small, and photoelectric conversion can be performed with high efficiency.

In addition, it is possible to reduce the thickness of the semiconductor layer (powder), which is the light absorption region, and thereby increase the light transmittance.This semiconductor photodetector can be inserted in the middle of the optical path. It is possible to detect optical signals without changing the optical path.This device can be made into a thin structure, so it can be incorporated into an integrated optical information processing circuit and mass-produced. .

[Embodiments of the invention]

As the light source of the optical signal, the luminescent wave key person uses 940OA (h sea 1
．． A GaAs light emitting diode (32 eV) is selected and a semiconductor photodetection device according to the present invention will be described below.

As a semiconductor material of P type and N shadow region, the wavelength is 87O
Gallium atomide UaAs (, l
]G = 1.43 eV), and In rx GaxAs (x = 0.75. F:
Gwl, 12 eV) was used. Figure 1 shows a semiconductor photodetector according to the present invention, with a concentration of 5x1016 m as a donor.
-' (D
An In0.2L Ga0.75 AS layer 22 is grown, and a concentration of 5XlOcm is further grown on it as an acceptor.
A P-type GaAs layer 23 doped with zinc is grown. The output electrodes for photocurrent or photovoltaic force are an electrode 24 formed on one main surface 26 and an electrode 25 formed on the other main surface 27.

Whether photocurrent or photovoltaic force is detected is determined by an external detection circuit.) As with conventional PN junction photodiodes, photovoltaic force can be detected by reducing external impedance. FIG. 1 shows a device that detects light without changing the optical path of light, and the metal electrodes are removed from the parts on the two main surfaces where light is input and output. The light transmittance of the light incident on the main surface 26 reaching the main surface 27 is the light absorption layer (a layer) 2
The thickness of the a layer can be controlled by the thickness of 4.
By setting it to 00OA, a light transmittance of 60% or more was obtained.

[Other embodiments of the invention]

In the above embodiments, a photodetector made of a semiconductor material mainly made of GaAs has been described for the case where a GaAs light emitting diode is used. However, if the wavelength of the light to be handled is different, please refer to the claims W and X of the claims. A combination of semiconductor materials that satisfies the conditions described above can be used. Although the semiconductor material of the P shadow region is the same as the semiconductor material of the N shadow region in the above-described embodiment, it may be the same as the semiconductor material of the N shadow region as long as it satisfies the conditions stated in claim 1. It may be different from the semiconductor material. Further, although an n-type semiconductor is used in the embodiment for the light absorption layer shown in FIG. 22, a p-type semiconductor may also be used. The light incident surface may be the main surface 26 in FIG. 1 or the main surface 27 on the opposite side. In Figure 1, the traveling directions of the incident light and the transmitted light are the same, but the main surface on the opposite side to the incident side may be used as a reflecting surface, or as shown in Figure 2. A reflective surface may be provided near the main surface on the opposite side to the main surface on the incident side to reflect the incident wave and also perform light detection at the same time.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining a light transmission type semiconductor photodetection device which is an embodiment of the present invention, and FIG. 2 is a diagram for explaining a light reflection type semiconductor photodetection device showing another embodiment of the present invention. diagram,
FIG. 3 is a diagram for explaining a light transmission type detection device according to the prior art. 1. Incident light, 2. ...output light, 3. ···reflected light. 4, . . . half mirror 15, . . photodetector, 21.
33...N-type semiconductor substrate, 22.32. ...
Light absorption layer, 23.33. ...P-type semiconductor layer,
24.25.34.35. ...electrode, 26.36.
...One main surface, 27.37. ...Other main surface, 38. ...Light reflecting plate. Figure 1 Figure 2 Figure 8

Claims (3)

[Claims] (1) On a semiconductor substrate (1) of the first conductivity type whose forbidden band (energy band gap E_G) is larger than the energy hν of the input destination, E_G is smaller than hν and the impurity concentration is 1×10^1^9 cm^ −^3 Semiconductor layer lower than 3 (2
) is formed on the semiconductor layer, E_G is larger than hν,
A semiconductor layer (8) having a conductivity type opposite to that of the semiconductor substrate (1).
1. A light-transmissive semiconductor photodetecting device, characterized in that it has a photodetecting section formed by forming a semiconductor device with a light transmittance of 50% or more from one principal surface to the other principal surface. (2) The semiconductor photodetecting device according to claim 1, wherein light incident from one principal surface is transmitted out of the other principal surface. (3) A light-transmissive semiconductor photodetector according to claim 1, characterized in that a light-reflecting surface is provided on or near the main surface opposite to the light-incident surface to reflect the incident light. Device.