JPH05251673A - Photodetector - Google Patents

Abstract

PURPOSE:To provide a high-speed photodetector array that does not suffer the optical loss due to the buffer layer between adjacent photodetector elements. CONSTITUTION:There are provided a photodetector array 1 including photodetector elements 3 for converting incident light into electrical signal, and a lens array 2 including lens elements adjoined to one another. Light incident each lens is converged to its corresponding photodetector element 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an array type photodetector, and more particularly to a photodetector suitable for obtaining high resolution with little optical loss.

[0002]

2. Description of the Related Art A conventional array type photodetector will be described with reference to the drawings. A conventional array type photodetector is shown in FIG. In this photodetector, light receiving elements each having an independent PN or PIN structure are arranged in a line. Each light receiving portion 102 is a buffer layer 1
It is electrically isolated by 05 and operates the same as an individual photodetector. Reference numeral 103 is a first electrode provided so as to surround the light receiving portion 102, and 104 is a second electrode. By applying a voltage between the first electrode and the second electrode, a current proportional to the optical signal detected by the light receiving unit 102 is extracted. FIG. 9 shows an example of a single photodetector (PIN-PD) that can be used in the long wavelength band. This is a PIN structure in which n ~ InGaAs and p + InGaAs are grown on an n + InP substrate. Light passes through the p-type semiconductor region and reaches n to InG
It is absorbed in the aAs layer. As an application example using such a photodetector array, there is a displacement sensor disclosed in the literature (Aizawa et al., Sensing Technology Using Optical Waveguide and Neural Network, Proceedings of Laser Society of Japan, p. 233, 1991). The structure of this displacement sensor is shown in FIG. In the figure, the light emitted from the movable object 114 is input to the multimode optical waveguide 111. Multimode optical waveguide 111
Then, a plurality of modes are excited, and the emission pattern thereof becomes a complicated interference pattern. When the movable object is displaced, the incident condition of light on the multimode optical waveguide changes, and the excited mode distribution also changes. The emission pattern from the multimode optical waveguide is photoelectrically converted by the photodetector array 112 and input to the neural network 113. The neural network 113 determines the displacement of the movable object from the change in the emission pattern. In this case, the photodetector array is used to detect the emission pattern from the waveguide.

[0003]

In the structure of the conventional photodetector, the buffer layer is provided to electrically separate the electrode elements, and the light incident on the buffer layer is not converted into an electric signal. There was a problem that it resulted in light loss. Further, in the case of the above-mentioned application example, there is a problem that the detection capability of the pattern is deteriorated because the portion of the emission pattern that enters the buffer layer cannot be detected.
In view of such problems, an object of the present invention is to provide a high-speed photodetector array having no light loss due to the buffer layer existing between the individual light receiving parts.

[0004]

In order to achieve the above-mentioned object, a photodetector of the present invention is provided with, for example, as shown in FIG.
A lens array 2 is provided together with a photodetector array 1 having a plurality of light receiving portions 3 for converting an incident optical signal into an electric signal, and the lens array 2 is composed of a plurality of lens elements arranged without a gap between them. A configuration is provided in which all the light incident on each of the elements is condensed on each of the corresponding light receiving portions. Here, if the lens array is formed on the substrate of the photodetector array, as shown in FIG. 2A, for example, optical alignment can be automatically formed. preferable. Alternatively, in this case, it is more preferable to form the lens array by a Fresnel lens as shown in FIG.

[0005]

According to the structure of the present invention, the incident light pattern is guided to the corresponding light receiving portion by the lens array.
The carriers generated in the light receiving portions are captured by the electrodes installed in each light receiving portion, and a current flows through the electrodes. Since the magnitude of the current is proportional to the intensity of light, it is possible to know the intensity distribution of light from the electrical signal distribution obtained from each electrode. According to the present invention, all the light incident from the lens array is condensed on the light receiving parts, and the light is not guided to the buffer layer existing between the light receiving parts, so that the light loss is small and high resolution can be obtained. Will also be possible. If the lens array is formed on the substrate of the photodetector, the optical alignment can be automatically formed. Further, if the lens array is composed of Fresnel lenses, the lenses can be made thin, and a preferable structure can be realized.

[0006]

FIG. 1 shows the first embodiment of the present invention. Here, 1 is a photodetector array, 2 is a lens array, 3 is a light receiving portion of the photodetector array, and 4 is an electrode for extracting an electric signal. The lens array is arranged on the light receiving unit. The optical signal is divided by the lens array 2 according to the spatial distribution of the optical signal and is guided to the light receiving surface 3 of the corresponding photodetector array. At this time, even if there is a gap between the light receiving surfaces, no gap is provided between the lens elements of the lens array, and all the light incident from each lens element is configured to enter the corresponding light receiving portion. ing. Therefore, the optical signal is guided to each light receiving portion of the photodetector array without loss. The photoelectrically converted electrical signal is obtained from the electrodes. Since the magnitude of the current appearing in the electrode is proportional to the incident light intensity, the light intensity distribution can be obtained from the signal intensity of the electrode element.

2 and 3 show a second embodiment of the present invention. FIG. 2A is a view of the photodetector of the present invention when viewed from the light incident side, and FIG. 2B is a view when viewed from the electrode side formed on the substrate. In addition, FIG.
2A is a sectional view of the substrate shown in FIG. 3B (this is simply referred to as an ab sectional view), and FIG.
A sectional view of d (this is simply referred to as a sectional view of cd) is shown. Reference numeral 11 is a substrate, 12 is a lens, 13 and 14 are intrinsic semiconductor layers, 15 is a light receiving portion, 16 is an electrode layer, 17 is a first electrode portion, 18 is a second electrode portion, and 19 is a buffer layer. .. The substrate 11 may be either an n-type semiconductor or a p-type semiconductor. It is assumed that the light receiving portion 15 is a p-type semiconductor when the substrate 11 is an n-type semiconductor and an n-type semiconductor when the substrate 11 is a p-type semiconductor. FIG. 5 shows the case where the n-type semiconductor InP is the substrate. Light incident from the substrate side is refracted by the lens. Since the band gap of the substrate is larger than the energy of the incident light, the light passes through the substrate and reaches the light receiving section. The carriers generated in the light receiving portion diffuse toward the electrode element of the first electrode portion, and a current flows. Here, a potential for absorbing carriers is applied to each electrode element of the first electrode portion in advance. Since the magnitude of the current is proportional to the intensity of the incident light, the intensity distribution of the incident light can be detected from the magnitude of the electric signal of each electrode element. In this configuration, since the light is condensed by the lens array, the light can be guided to the corresponding light receiving portion, and there is no light loss due to the buffer layer between the light receiving portions. Further, since the lens array is formed directly on the substrate, optical alignment is unnecessary. The lens formed on the substrate can be manufactured by processing it into a lens shape by Ar ion etching or the like, or can be manufactured by giving a refractive index distribution by doping.
In addition, Fresnel lenses and CGH (Computer Generated
It is also possible to make a lens by Hologram). It is also possible to reduce the light loss due to surface reflection by mounting a non-reflective coating film on the upper surface of the light receiving portion.

FIG. 4 shows a third embodiment of the present invention. Also in this case, the cross-sectional view is taken along the line ab. The operation as the photodetector is the same as that of the second embodiment. The difference from the second embodiment is that the electrode layer is made of the same semiconductor material as that of the light receiving portion, so that the manufacturing process is simplified.

FIG. 5 shows a fourth embodiment of the present invention. The operation of the photodetector is the same as that of the first embodiment. Second
The lens array portion in the above embodiment is composed of a Fresnel lens. In this case, the lens can be thin.

FIG. 6 shows a fifth embodiment of the present invention. When viewed from the light incident side, the lenses are two-dimensionally arranged on the substrate. When viewed from the electrode side on the back surface, the first electrode portions are two-dimensionally arranged. With this configuration, the two-dimensional spatial distribution of light can be detected.

FIG. 7 shows a sixth embodiment of the present invention. When viewed from the light incident side, the lenses are two-dimensionally arranged on the substrate. When viewed from the electrode side on the back surface, the first electrode portions are two-dimensionally arranged. Further, the second electrode portion is formed so as to surround the element of the first electrode portion. Thereby, the two-dimensional spatial distribution of light can be detected. In this structure, each element of the first electrode portion is electrically insulated, and electrical crosstalk is reduced.

[0012]

According to the present invention, since the light is guided to the corresponding light receiving portion by the lens array, the light is not guided to the buffer layer between the light receiving elements, so that the light pattern is detected without light loss. be able to. Moreover, since the lens array and the photodetector array are integrated, optical alignment between the lens array and the photodetector array is automatically performed.

[Brief description of drawings]

FIG. 1 is a diagram of a first embodiment of the present invention.

FIG. 2 is a diagram of a second embodiment of the present invention.

FIG. 3 is a sectional view of a second embodiment of the present invention.

FIG. 4 is a diagram of a third embodiment of the present invention.

FIG. 5 is a diagram of a fourth embodiment of the present invention.

FIG. 6 is a diagram of a fifth embodiment of the present invention.

FIG. 7 is a diagram of a sixth embodiment of the present invention.

FIG. 8 is a conventional example diagram.

FIG. 9 is a diagram showing an example of a PIN photodiode.

FIG. 10 is an application example diagram using a photodetector array.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Photodetector array 2 ... Lens array 3 ... Light receiving part 4 ... Electrode 11 ... Semiconductor substrate 12 ... Lens 13 ... Intrinsic layer 1 14 ... Intrinsic layer 2 15 ... Light receiving part 16 ... Electrode layer 17 ... First electrode part 18 ... second electrode part 19 ... buffer layer 101 ... substrate 102 ... light receiving part 103 ... first electrode 104 ... second electrode 105 ... buffer layer 111 ... multimode optical waveguide 112 ... photodetector array 113 ... neural network 114 … Movable object

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Takao Matsumoto 1-1-6 Uchisaiwai-cho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation (72) Masahiro Yuda 1-1-6 Uchisai-cho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation

Claims (3)

[Claims] 1. A photodetector having a photodetector array having a plurality of photodetectors and converting an optical signal incident on the photodetectors into an electric signal, the photodetector array including a lens array, The lens array is composed of a plurality of lens elements arranged without a gap between each other, and is provided with a configuration for condensing all the light incident on each of the lens elements on the corresponding respective light receiving portions. . 2. The photodetector according to claim 1, further comprising a lens array formed on a substrate of the photodetector array. 3. The photodetector according to claim 1 or 2, wherein the lens array is composed of Fresnel lenses.