JP2008085265A - Quantum well type optical detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a quantum well type optical detector so designed that only by adding a simple alteration to a structure of the quantum well type optical detector for selectively operating a plurality of laminated MQW layers, and optical absorption in a non-selected MQW layer is not influenced by light incident on a selected MQW layer. <P>SOLUTION: A first MQW layer 33 composed of a multiple quantum well vertically sandwiched between n-type contact layers 32 and 34, for absorbing light of a prescribed wavelength, and a second MQW layer 37 vertically sandwiched between n-type contact layers 36 and 38, for absorbing the light of a wavelength different from the wavelength of the light absorbed by the first MQW layer 33, are laminated on each other via a p-type GaAs intermediate layer 35. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a photodetector that generates a photocurrent according to the amount of incident light, and relates to an improvement of a quantum well photodetector that performs light absorption by a multiple quantum well (MQW) layer.

  FIGS. 16A and 16B are main part explanatory views showing a conventional quantum well infrared detector, in which FIG. 16A shows a cut side of the main part, FIG. 16B shows a cut side of the main part of MQW, and FIG. Respectively.

In the figure, 1 is an n-type GaAs contact layer, 2 is an MQW layer, 2B is a barrier, 2W is a quantum well, 3 is an n-type GaAs contact layer, 4 is a negative side (ground side) electrode, and 5 is a positive side electrode. , E _c indicate the lower end of the conduction band, respectively.

  In this detector, an electron photoexcited from the ground level to the excited level by light absorption in the quantum well 2W is biased to extract out of the quantum well 2W and generate a photocurrent.

  The wavelength of the optical response depends on the energy difference between the quantum levels, which is the thickness of the quantum well 2W and the energy height of the barrier 2B in the MQW layer 2 (depending on the material composition of the barrier 2B). It depends on.

  Therefore, the layer thickness of the quantum well 2W and the composition of the barrier 2B are adjusted in accordance with the target wavelength, but the response wavelength as designed is not always obtained due to the influence of manufacturing errors and the like.

  In order to cope with such problems, MQW layers having different structures, that is, MQW layers having different response wavelengths are prepared and laminated in advance, and an MQW layer capable of obtaining a response close to the target wavelength is obtained. Selective use is performed (see, for example, Japanese Patent No. 3777889).

  FIG. 17 is an explanatory view of a main part showing a quantum well infrared detector in which MQW layers having different response wavelengths are stacked. In FIG. 17, 11 is an n-type GaAs contact layer, 12 is a first MQW layer, and 13 is a first MQW layer. An n-type GaAs contact layer, 14 is a second MQW layer, 15 is an n-type GaAs contact layer, 16 is a negative side (ground side) electrode, 17 is a bias voltage application electrode, and 18 is a positive side electrode. .

  The illustrated quantum well infrared detector has a structure in which two of the first MQW layer 12 and the second MQW layer 14 are laminated, and the response wavelength of the first MQW layer 12 and the second MQW layer. The MQW layer is designed so as to be different from the response wavelength of 14 and can obtain a response close to the target wavelength (see, for example, Japanese Patent No. 3777889).

  18A and 18B are explanatory views of a principal part showing a quantum well infrared detector for explaining the problems of the invention disclosed in Patent Document 1, wherein FIG. 18A is a sectional view of the principal part, and FIG. (C) shows the main energy band of the second MQW layer 14, respectively.

  In the figure, 19 is a switch for turning on and off the voltage to the first MQW layer 12, and 20 is a switch for turning on and off the voltage to the second MQW layer 14. In the figure, the switch 19 is open, that is, the applied voltage to the first MQW layer 12 is off, and the switch 20 is closed, that is, the applied voltage to the second MQW layer 14 is It shows that it is on.

  FIG. 19 is a diagram showing the relationship between the detection light wavelength and sensitivity for explaining the problems of the invention disclosed in Patent Document 1. The horizontal axis represents wavelength (μm), and the vertical axis represents sensitivity. Yes, symbol 12 is the response characteristic of the first MQW layer 12, symbol 14 is the response characteristic of the second MQW layer 14, 21 is the target wavelength (dashed curve), 22 is the crosstalk region (dashed circle), respectively Show.

  The detector shown in FIG. 18 has a configuration in which two MQW layers 12 and 14 having a setting close to a predetermined target wavelength are stacked, and therefore, wavelength crosstalk between the optical response spectra of the two MQW layers 12 and 14. It is easy to produce.

  That is, as shown in FIG. 19, a bias voltage is applied only to the second MQW layer 14 showing a response close to the target to generate a photocurrent, and the bias current is turned off for the first MQW layer 12 to generate a photocurrent. In the MQW layer of the first MQW layer 12, the electrons photoexcited from the ground level of the quantum well are again trapped in the quantum well, so that light absorption always occurs. .

Accordingly, in the wavelength region of the crosstalk region 22, the light incident on the second MQW layer 14 is attenuated due to the light absorption on the first MQW layer 12 side, and the sensitivity in this portion is The problem of degrading occurs.
Japanese Patent No. 3777889

  In the present invention, only a simple modification is made to the structure of a quantum well photodetector that selectively operates a plurality of stacked MQW layers, and the light incident on the selected MQW layer is not selected in the MQW layer. Make sure that light absorption is not affected.

  In the quantum well-type photodetector according to the present invention, the first multiple quantum well layer composed of multiple quantum wells that are sandwiched between upper and lower one conductivity type contact layers and absorb light of a required wavelength, A second multiple quantum well layer composed of multiple quantum wells that are sandwiched between conductive type contact layers and absorb light having a wavelength different from the wavelength of light absorbed by the first multiple quantum well layer is a semiconductor having a conductivity type opposite to that of the contact layer. It comprises the structure laminated | stacked through the layer, It is characterized by the above-mentioned.

  By adopting the above-mentioned means, it is possible to selectively set the MQW layer adapted to the wavelength to be detected among a plurality of stacked MQW layers having different sensitivity wavelengths to an operating state with a simple configuration, It is possible to sufficiently suppress the decrease in sensitivity due to crosstalk between wavelengths in the stacked MQW layer, and furthermore, it is a photodetector that has such excellent characteristics, but has a structure that is easy to manufacture. Therefore, its productivity is good.

  FIG. 1 is an explanatory side view of a principal part showing a basic quantum well photodetector according to the present invention. In FIG. 1, 32 is an n-type GaAs contact layer, 33 is a first MQW layer, and 34 is a first MQW layer. n-type GaAs contact layer, 35 p-type GaAs intermediate layer, 36 n-type GaAs contact layer, 37 second MQW layer, 38 n-type GaAs contact layer, 39 positive electrode, and 40 and 41 negative side (Ground side) electrode, 42 is a positive electrode, and 43 and 44 are switches.

  In the illustrated quantum well type photodetector, when two MQW layers 33 and 37 are stacked, contact layers 32 and 34, contact layers 36 and 38 are provided above and below each MQW layer 33 and 37, and The contact layer 34 and the contact layer 36 have a structure in which a GaAs intermediate layer 35 having a conductivity type opposite to that of each contact layer, that is, a p-type is provided. Here, the p-type GaAs intermediate layer 35 generates an npn junction between the n-type GaAs contact layer 34 and the n-type GaAs contact layer 36, and reversely biases the npn junction to prevent current from flowing. It is intended to make it work, and is one of the important elements in the present invention.

  In addition, electrodes for applying a bias voltage from the outside are formed in the upper and lower contact layers 32 and 34 and the contact layers 36 and 38 in the two MQW layers 33 and 37, respectively, and accordingly in a total of four locations. The two electrodes 40 and 41 in the central portion selectively select either one of the two MQW layers 33 and 37 by selectively closing one of the switches 43 and 44. To be able to connect to the power supply.

  FIG. 2 is an energy band diagram for explaining the operation of the quantum well photodetector shown in FIG. 1, wherein (A) relates to the second MQW layer, and (B) relates to the first MQW layer. The parts indicated by the same symbols as those used in FIG. 1 represent the same or equivalent parts. In the figure, 33W and 37W indicate quantum wells, and white circles indicate electrons.

  In the quantum well photodetector according to the present invention, as described with reference to FIG. 1, two MQW layers 33 and 37 are stacked, and a bias voltage V is applied to the electrodes 39 and 42 at both ends thereof. In the electrodes 40 and 41, the switch 44 is turned on so that the MQW layer on one side, in the drawing, the electrode 41 of the contact layer 36 in contact with the MQW layer 37 is conductive, and the switch 43 of the MQW layer 33 is turned off. Yes.

  When the optical response spectrum characteristic of the MQW layer 37 is close to the target, the MQW layer 37 is in a normal operation state in the above connection state, and the electrons in the quantum well 37W as shown in FIG. Is photoexcited and flows into the contact layer 38, so that a photocurrent OC is generated.

  Further, in the MQW layer 33, a bias voltage is applied between the contact layer 36 under the MQW layer 37 and the lowermost contact layer 32, so that the npn junction and the MQW layer 33 are Are connected in series, and a bias voltage is applied.

  In this case, as seen in FIG. 2B, the photoexcited electrons are emitted from the quantum well 33W of the MQW layer 33 by the electric field, but thereafter, the inflow of electrons from the contact layer 36 is reverse biased. Since it is blocked by the npn junction in the state, no photocurrent is generated.

  That is, on the MQW layer 33 side, replenishment of electrons to the multiple quantum well 33W is interrupted, and electrons in the quantum well 33W are deficient, so that no light absorption occurs in the MQW layer 33.

  From the above-described operation, it can be understood that a decrease in sensitivity of the MQW layer 37 due to crosstalk on the MQW layer 33 side is suppressed.

  FIG. 3 is a side view for explaining a principal part of a semiconductor layer laminated structure for producing a quantum well type photodetector according to the present invention. Basically, the second layer is formed on a GaAs substrate 31 having a plane orientation (100). One MQW layer 51, an intermediate layer 52 for generating an npn junction, and a second MQW layer 52 are grown.

In the first MQW layer 51, an i-AlGaAs (Al composition = 0.255) barrier layer and an n-type GaAs well layer are repeatedly formed 20 times on an n-type GaAs layer having an impurity concentration of 1 × 10 ¹⁸ cm ^−3. It is a thing.

The intermediate layer 52 is formed by sequentially forming an n-type GaAs layer / p-type GaAs layer (impurity concentration of 5 × 10 ¹⁷ cm ⁻³ ) / n-type GaAs layer on the first MQW layer 51.

  The second MQW layer 53 is different from the first MQW layer 51 in the composition of i-AlGaAs (Al composition = 0.245).

  An n-type GaAs layer or the like is grown on the second MQW layer 53 to complete the wafer. Here, as a technique for crystal growth of the semiconductor layer, an MBE (Molecular Beam Epitaxy) method or a MOVPE (Metalorganic Vapor Phase Epitaxy) method may be applied.

  FIG. 4 to FIG. 11 are main parts showing a quantum well type photodetector in the process key points for explaining the process of manufacturing the quantum well type photodetector using the wafer produced by carrying out the crystal growth. FIG. 1 is a cut side view, and in the following description, reference is made to each of the above drawings, and FIG. 1 is shown for the configuration of the quantum well photodetector, and the first MQW layer 51, intermediate layer 52, and second MQW layer. 53 can be easily understood by referring to FIG. 3 as needed.

Refer to FIG. 4. In order to fabricate an optical coupler necessary for the quantum well photodetector, on the surface of the wafer including the first MQW layer 51, the intermediate layer 52, and the second MQW layer 53 described with reference to FIG. A diffractive structure (unevenness) is formed.

  That is, a GaAs layer is formed on the surface of the wafer via an AlGaAs layer (not shown because it is extremely thin; the same applies hereinafter), and the selective dry etching method is applied to the GaAs layer using the AlGaAs layer as an etching stopper. The diffraction structure 54 is formed by processing.

See FIG. 5. Contact holes A, B, and C are formed for contacting the electrodes to the n-type GaAs contact layers 36, 34, and 32, respectively. In this case, the InGaP layer (see FIG. 3) is used as an etching stopper, and the GaAs layer / AlGaAs layer is processed by applying a dry etching method.

  When the contact holes B and C are formed, dry etching stops at the InGaP layer as an etching stopper. Therefore, wet etching is performed using HCl as an etchant, and dry etching is performed again.

See FIG. 6. A SiON protective film 55 is formed on the entire surface including the inner walls of the contact holes A to C, and then the SiON protective film 55 in the ohmic electrode formation scheduled region is removed by applying a dry etching method, and then a lift-off method is performed. The electrodes 42, 41, 40 and 39 made of AuGe / Au are formed by application.

See FIG. 7. After applying the dry etching method and removing the SiON protective film 55 covering the diffraction structure 54, the lift-off method is applied to form the mirror electrode 56 made of TiW / Au.

See FIG. 8. The entire surface is covered with a SiON protective film 57, and a dry etching method is applied to remove the SiON protective film 57 at a location necessary to establish electrical connection with the electrodes 42 to 39 to expose a contact hole. .

See FIG. 9. By applying the sputtering method, a Ti / Pt film is formed on the entire surface, and then a mask for the wiring pattern is formed, and unnecessary portions are removed by applying the ion milling method. Wirings 62, 61, 60, 59 extending from ~ 39 through the contact holes to the surface are formed. Note that the wiring 62 and the wiring 59 are commonly connected at locations not shown in the figure.

See FIG. 10. By applying the dry etching method, the SiON protective film 55 in the region where the isolation trench for separating a large number of pixels is to be formed is removed, and then the second MQW that has been the base is removed. Etching of various semiconductor layers such as the layer 53, the intermediate layer 52, and the first MQW layer 51 is performed to form an element isolation groove 63 that divides the lowermost n-type GaAs contact layer 32. At this time, if dry etching is stopped at the InGaP layer as an etching stopper, the same method as described in the step of FIG. 5 is adopted, and the dry etching is performed while using the wet etching method using HCl as an etchant. To do.

Refer to FIG. 11 again. After the entire surface is covered with the SiON protective film 58, an In bump electrode 59 necessary for connection to the readout circuit is formed. For that purpose, the lift-off method may be applied after removing the SiON protective film 58 in the portion where the In bump electrode is to be formed.

  FIG. 12 is an explanatory view of the principal part showing the connection relation between the quantum well type photodetector and the readout circuit according to the present invention, and the parts indicated by the same symbols as those used in FIGS. 1 and 11 are the same or It shall represent the part with the same effect.

  In the figure, 71 is a readout circuit, 72 and 73 are switch transistors, 74 is a bias power supply input gate transistor, 75 is an integration capacitor, and 76 is a power reset transistor. The switching transistors 72 and 73 correspond to the switches 43 and 44 shown in FIG.

  The second MQW layer 53 and the first MQW layer 51 are designed so that the photoresponse peak wavelengths are obtained with 8.9 μm and 8.4 μm as standard, respectively, depending on the structure of the quantum well described with reference to FIG. Has been. If the desired peak wavelength when used as a photodetector is in the range of 8.6 ± 0.2 μm and the Al composition becomes large due to an error during manufacturing, the second MQW layer 53 side is activated, that is, Then, the switch 44 (transistor 73) is turned on. Conversely, when the Al composition becomes smaller, the first MQW layer 51 side is activated, that is, the switch 43 (transistor 72) is turned on.

  FIG. 13 is a diagram showing the relationship between the Al composition and the light absorption wavelength in the MQW layer. FIG. 13A shows the case of the present invention having two MQW layers, and FIG. 13B shows the conventional structure having one MQW layer. Each example is shown.

  In (A) of the figure, the numerical value on the left is the wavelength of light, and the range indicated by (1) in the bar graph on the right side of the numerical value is the change range of the photoresponse peak wavelength in the first MQW layer, The numerical value on the right side of the bar graph corresponds to the numerical value of the Al composition (0 is 0.245, and each numerical value is multiplied by 0.01 and the value obtained by adding 0.245 to the Al composition value). The range indicated by (2) of the bar graph in FIG. 2 is the change range of the photoresponse peak wavelength in the second MQW layer, and the numerical value on the right side of the bar graph is the corresponding Al composition value (0 is 0.255). The value obtained by multiplying each numerical value by 0.01 and adding to 0.245 is the Al composition value), and the two curves on the right side of the numerical values indicate the light absorption of the first MQW layer and the second MQW layer. It is a diagram showing a characteristic. Note that (B) in the figure can be viewed in the same way as (A) in the figure except for the point in the figure in the case where there is one MQW layer.

  In the case of the present invention, by selectively using the first MQW layer and the second MQW layer, as can be seen from FIG. In the range of -4 to +5, either the first or second MQW layer can function as a photodetector having a desired peak wavelength.

  In the ordinary quantum well type photodetector, that is, the one described with reference to FIG. 16, as can be seen from FIG. 13B, when the quantum well structure is manufactured with the center peak wavelength set to 8.6 μm, It is only possible to satisfy the peak wavelength = 8.6 ± 0.2 μm when the Al composition is in the range of −2 to +2. Therefore, according to the present invention, it can be understood that the tolerance for wafer manufacturing error, that is, Al composition error, has been greatly expanded.

  FIG. 14 is a plan view of the principal part showing another example of the quantum well type photodetector according to the present invention, and the parts indicated by the same symbols as those used in FIGS. 4 to 11 are the same or effective. It shall represent a part.

  In the figure, reference numeral 81 denotes one quantum well photodetector, that is, one pixel electrically separated by the element isolation groove 63 shown in FIG. Is provided with two MQW layers stacked as described above.

  Each pixel 81 is provided with the contact holes A, B, and C described with reference to FIG. 5, and the wiring drawn out from the contact hole A is commonly connected by the wiring 82 across the bottom of the element isolation groove 63. The wiring 82 is all led out to one side in the vicinity of the detector and connected to the In bump 65A, and the wiring drawn out from the contact hole B is also commonly connected by the wiring 83 that extends over the bottom of the separation groove 63. Similarly, all are led out to the other side in the periphery and connected to the In bump 65B.

  It is easy to form the wiring 82 or 83, and the order of the process described with reference to FIG. 9 and the process described with reference to FIG. 10 are switched, that is, the wiring forming process is performed after the element isolation groove 63 is formed. This can be realized easily.

  In this way, the lead-out wiring from the contact holes A and B can be shared so as to be connected to the readout circuit in a lump at the periphery, and only one In bump is formed in each individual pixel. Can be achieved.

  FIG. 15 is a plan view of an essential part for explaining a case where the photodetector described with reference to FIG. 14 is connected to a readout circuit. FIG. 15 (A) shows a bump group in the periphery of the readout circuit, and FIG. Each of the bump groups in the periphery of the photodetector is shown.

  The interval between the bumps 89A on one side of the readout circuit shown in FIG. 15A and the bumps 89B on the other side facing each other is the bump provided in the photodetector shown in FIG. Compared to the distance between 65A and bump 65B, at least one bump is displaced. Accordingly, when the respective bump sides of the readout circuit and the photodetector are opposed to each other and, for example, the bump 89A and the bump 65A are connected, the bump 89B and the bump 65B are not connected, so the circuit is open. In the illustrated example, the bump 65B side is connected.

  As described above, in the second embodiment, it is possible to select which of the first MQW layer and the second MQW layer is in an operable state only by shifting the bonding position of the readout circuit and the photodetector. Therefore, it is not necessary to separately provide the switches 43 and 44 described with reference to FIG.

  Which of the common wirings 82 and 83 is connected to the readout circuit depends on whether the first MQW layer and the second MQW layer are previously connected in a state before flip-chip connection of a chip in which a large number of pixels are arranged and the readout circuit chip. It is only necessary to examine the element characteristics and select a connection that can drive the MQW layer side close to the desired wavelength characteristic as usual.

  Since the present invention can be implemented in many forms including the above-described embodiment, it will be exemplified as an additional note hereinafter.

(Appendix 1)
A first multiple quantum well layer composed of multiple quantum wells sandwiched between upper and lower one conductivity type contact layers and absorbing light of a required wavelength, and a first multiple quantum well layer sandwiched between upper and lower one conductivity type contact layers A second multi-quantum well layer composed of a multi-quantum well that absorbs light having a wavelength different from the wavelength of the light to be emitted is laminated via a semiconductor layer having a conductivity type opposite to that of the contact layer. Quantum well type photodetector.

(Appendix 2)
An electrode formed on the substrate-side one conductivity type contact layer in the first multiple quantum well layer and the surface-side one conductivity type contact layer in the second multiple quantum well layer and connected to the same bias power source; One of the surface-side one conductivity type contact layer in the multiple quantum well layer and the substrate side one conductivity type contact layer in the second multiple quantum well layer are connected to a potential different from that of the bias power source, In addition, the quantum well photodetector according to (Appendix 1), wherein the other is provided with an electrode opened from the potential.

(Appendix 3)
In an array in which a plurality of pixels including a stacked first multiple quantum well layer and a second quantum well layer are arranged, and a connection configuration of a readout circuit that reads out a photocurrent signal from the pixel,
Wirings commonly connecting the electrodes in the surface side contact layer of the first multiple quantum well layer in the array, and the electrodes in the substrate side contact layer of the second multiple quantum well layer in the array The quantum well photodetector according to (Appendix 1) or (Appendix 2), characterized in that a common interconnect is provided, and any one of the interconnects is connected to a readout circuit.

(Appendix 4)
Any one of (Appendix 1) to (Appendix 3) is provided with a switch interposed between each common wiring and the readout circuit and connecting any one of the common wirings to the readout circuit. Quantum well type photodetector.

(Appendix 5)
The quantum well and the barrier in the multiple quantum well layer are made of a material selected from GaAs, InAs, AlAs, InP, GaP, AlP and mixed crystals thereof (Appendix 1) to (Appendix 4) The quantum well type photodetector according to any one of the above.

(Appendix 6)
In manufacturing the quantum well type photodetector of (Appendix 1) to (Appendix 5),
When connecting either the first multiple quantum well layer or the second multiple quantum well layer to the readout circuit, a step of measuring a spectral response characteristic of each multiple quantum well layer in advance and selecting an appropriate multiple quantum well layer A method for producing a quantum well photodetector, comprising:

It is principal part cutting side explanatory drawing showing the basic quantum well type | mold photodetector by this invention. It is an energy band diagram for demonstrating operation | movement of the quantum well type | mold photodetector seen by FIG. It is principal part side explanatory drawing showing the semiconductor layer laminated structure for producing the quantum well type | mold photodetector by this invention. 3 is a sectional side view of a principal part representing a quantum well photodetector in a process point for explaining a process of manufacturing a quantum well photodetector using a wafer produced by performing the crystal growth explained with reference to FIG. FIG. 3 is a sectional side view of a principal part representing a quantum well photodetector in a process point for explaining a process of manufacturing a quantum well photodetector using a wafer produced by performing the crystal growth explained with reference to FIG. FIG. 3 is a sectional side view of a principal part representing a quantum well photodetector in a process point for explaining a process of manufacturing a quantum well photodetector using a wafer produced by performing the crystal growth explained with reference to FIG. FIG. 3 is a sectional side view of a principal part representing a quantum well photodetector in a process point for explaining a process of manufacturing a quantum well photodetector using a wafer produced by performing the crystal growth explained with reference to FIG. FIG. 3 is a sectional side view of a principal part representing a quantum well photodetector in a process point for explaining a process of manufacturing a quantum well photodetector using a wafer produced by performing the crystal growth explained with reference to FIG. FIG. 3 is a sectional side view of a principal part representing a quantum well photodetector in a process point for explaining a process of manufacturing a quantum well photodetector using a wafer produced by performing the crystal growth explained with reference to FIG. FIG. 3 is a cut side view of a main part representing a quantum well photodetector in a process point for explaining a process of manufacturing a quantum well photodetector using a wafer produced by performing the crystal growth described with reference to FIG. FIG. 3 is a sectional side view of a principal part representing a quantum well photodetector in a process point for explaining a process of manufacturing a quantum well photodetector using a wafer produced by performing the crystal growth explained with reference to FIG. FIG. It is principal part explanatory drawing showing the connection relation of the quantum well type | mold photodetector and read-out circuit by this invention. It is a diagram showing the relationship between the Al composition and the light absorption wavelength in the MQW layer. It is a principal part top view showing the other example of the quantum well type | mold photodetector by this invention. It is a principal part top view for demonstrating the case where the photodetector demonstrated about FIG. 14 is connected with a readout circuit. It is principal part explanatory drawing showing the conventional quantum well type | mold infrared detector. It is principal part explanatory drawing showing the quantum well type | mold infrared detector which laminated | stacked MQW layer from which a response wavelength differs. It is principal part explanatory drawing showing the quantum well type | mold infrared detector for demonstrating the problem of the invention disclosed by patent document 1. FIG. It is a diagram showing the relationship between the detection light wavelength and sensitivity for explaining the problem of the invention disclosed in Patent Document 1.

Explanation of symbols

32 n-type GaAs contact layer 33 first MQW layer 34 n-type GaAs contact layer 35 p-type GaAs intermediate layer 36 n-type GaAs contact layer 37 second MQW layer 38 n-type GaAs contact layer 39 positive side electrodes 40 and 41 negative Side (ground side) electrode 42 Positive side electrode 43 and 44 Switch

Claims (5)

  A first multiple quantum well layer composed of multiple quantum wells that are sandwiched between upper and lower one conductivity type contact layers and absorbs light of a required wavelength, and a first multiple quantum well layer sandwiched between upper and lower one conductivity type contact layers And a structure in which a second multiple quantum well layer composed of multiple quantum wells that absorb light having a wavelength different from the wavelength of light to be absorbed is stacked via a semiconductor layer having a conductivity type opposite to that of the contact layer. Quantum well type photodetector. An electrode formed on the substrate-side one conductivity type contact layer in the first multiple quantum well layer and the surface-side one conductivity type contact layer in the second multiple quantum well layer and connected to the same bias power source; One of the surface-side one conductivity type contact layer in the multiple quantum well layer and the substrate side one conductivity type contact layer in the second multiple quantum well layer are connected to a potential different from that of the bias power source, 2. The quantum well photodetector according to claim 1, wherein the other is provided with an electrode opened from the potential. In an array in which a plurality of pixels including a stacked first multiple quantum well layer and a second quantum well layer are arranged, and a connection configuration of a readout circuit that reads out a photocurrent signal from the pixel,
Wirings commonly connecting the electrodes in the surface side contact layer of the first multiple quantum well layer in the array, and the electrodes in the substrate side contact layer of the second multiple quantum well layer in the array The quantum well photodetector according to claim 1 or 2, wherein a wiring connecting the two is commonly provided, and one of the wirings is connected to a readout circuit. The quantum well according to any one of claims 1 to 3, further comprising a switch interposed between each common wiring and the readout circuit and connecting any one of the common wirings to the readout circuit. Type light detector. 5. The quantum well and the barrier in the multiple quantum well layer are made of a material selected from GaAs, InAs, AlAs, InP, GaP, AlP and mixed crystals thereof. The quantum well type photodetector according to claim 1.

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