JP2005123513A - Photodetector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photodetector which is monolithically integrated with a waveguide composed of silicon and having a small element size. <P>SOLUTION: A pn junction is formed in a silicon core by constituting the silicon core with a p-type silicon core 102 and an n-type silicon core 103. A reverse-bias voltage is applied to the pn junction with a power supply 110, and the electron-hole pairs (carriers) generated by propagating a light with the light intensity of a predetermined value or more in the silicon core are taken out from a side cladding layer 104a connected to the p-type silicon core 102 and a side cladding layer 104b connected to the n-type silicon core 103 as an electric signal. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical waveguide type photodetector required for optical processing such as optical communication, optical information processing, and optical sensing.

  Recent advances in optoelectronic technology are remarkable, and this field extends to sensing and computing, centering on optical communications. Such optical parts used in the field of optoelectronics have a drawback that they are larger than electric parts. A general semiconductor laser light source has a size of several hundreds of micrometers, and has a size of several tens of millimeters for an optical circuit made of a silicon oxide compound or a silicon nitride compound. Therefore, studies have been made to reduce the size of optical components to a size that enables high-density integration.

  In such studies, the active elements such as light sources, switches, amplifiers, modulators, and light receivers are in a state where basic studies on miniaturization using photonic crystals have been made. On the other hand, in the optical waveguide, the dimension of the cross section is made 500 nm or less and the bending radius can be several μm by the core using silicon. In electronic devices using silicon, many studies have been made for miniaturization, and nanometer-sized elements have been realized.

  However, optical parts using silicon are limited to the above-described minute waveguides, MEMS optical switches, and the like. Silicon is an indirect transition semiconductor, and is transparent to light having a wavelength of 1.2 to 1.5 μm used in optical communication and optical information processing, and has no interaction with light. For this reason, as described above, a fine active element using silicon has not been realized.

  On the other hand, conventionally, an autocorrelator using two-photon absorption of a silicon photodiode (see Non-Patent Document 1), an autocorrelator using a silicon CCD camera (see Non-Patent Document 2), and two-photon absorption of a silicon photodiode are used. There are also reports of practical devices and apparatuses such as a reflectometer (see Non-Patent Document 3). These are technologies that attempt to use silicon devices that have been used as optical devices in the visible region with light having a wavelength of 1.3 to 1.5 μm.

The applicant has not yet found prior art documents related to the present invention by the time of filing other than the prior art documents specified by the prior art document information described in this specification.
C.Xu, JMRoth, WHKnox and K. Bergman, "Ultra-sensitive autocorrelation of 1.5μm light with single photon counting silicon avalanche photodiode", ELECTRONICS LETTERS, Vol.38, No.2, pp86-88, 17th January 2002. Dmitriy Panasenko and Yeshaiahu Fainman, "Interferometric correlation of infrared femtosecond pulses with two-photon conductivity in a silicon CCD", APPLIED OPTICS, Vol.41, No.18, pp3748-3752,20 June 2002. Y Tanaka, N Sako, T Kurokawa, H Tsuda, and M Takeda, "Profilometry based on two-photon absorption in a silicon avalanche photodiode", OPTICS LETTERS, Vol.28, No.6, pp402-404, 15 March 2003.

  However, the above-described optical device using silicon utilizing two-photon absorption has a large element size and requires a large device group, and miniaturization of these devices has not been studied.

  Therefore, conventionally, in order to obtain a fine active element that detects light having a wavelength in the range of 1.1 to 2.2 μm, an element made of a compound semiconductor such as a gallium arsenide compound or an indium phosphorus compound is used. It was supposed to be. For this reason, there is a problem that an integrated device in which a fine waveguide using a silicon core and the active element are integrated monolithically cannot be easily obtained.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a photodetector that can be monolithically integrated with a waveguide made of silicon with a small element size.

In the photodetector according to the present invention, a p-type region and an n-type region are formed so that a pn junction surface extends in the waveguide direction, and a dimension in at least one direction of a cross section is 500 nm or less. A power source that applies, for example, a reverse bias voltage between the p-type region and the n-type region of the core, an ammeter that measures a current flowing between the p-type region and the n-type region of the core, At least a cladding disposed around the core and having a refractive index lower than that of silicon is provided.
In this photodetector, when the intensity of light propagating through the core exceeds a predetermined value, carriers are generated by two-photon absorption (multiphoton absorption) in the core, and the resulting current is measured by an ammeter.

  In the photodetector, the cladding includes a first cladding layer made of a conductive material in contact with the p-type region of the core, a second cladding layer made of a conductive material in contact with the n-type region of the core, and the first cladding. What is necessary is just to be comprised from the 3rd cladding layer and the 4th cladding layer which consist of an insulating material arrange | positioned so that a core may be pinched | interposed so that a layer and a 2nd cladding layer may be insulated-separated. With this configuration, it is possible to apply a bias voltage to the p-type region and the n-type region while suppressing conductor loss in the core, and to measure a current due to carriers generated by two-photon absorption.

  In the photodetector, the first clad layer and the second clad layer may be disposed between the third clad layer and the fourth clad layer so as to face each other with the core interposed therebetween. The clad layer may be sandwiched between the first clad layer and the second clad layer and disposed opposite to each other with the core therebetween. The first cladding layer and the second cladding layer can be made of any material selected from a zinc oxide-based compound or an indium oxide-based compound.

  As described above, according to the present invention, since the photodetector is constituted by the waveguide formed by the silicon core, the structure is simple and can be easily miniaturized, and other optical circuits made of the silicon core can be used. Is very easy to connect. As a result, according to the present invention, it is possible to provide an excellent effect that a photodetector that can be monolithically integrated with a waveguide made of silicon with a small element size can be provided.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[Embodiment 1]
FIG. 1 is a perspective view schematically showing a configuration example of a photodetector in the embodiment of the present invention.
The photodetector includes a p-type silicon core (p-type region) 102 and an n-type silicon core (n-type region) 103 disposed adjacent to each other on the lower cladding layer 101. The p-type silicon core 102 and the n-type silicon core 103 form a pn junction surface in a direction perpendicular to the main surface of the lower cladding layer 101.

  The cross section of the silicon core composed of the p-type silicon core 102 and the n-type silicon core 103 has a dimension in at least one direction of 500 nm or less. For example, the cross section of the silicon core may have a width of 1 μm in the horizontal direction of FIG. 1 and a height of 500 nm in the vertical direction of the paper. In this case, each cross section of the p-type silicon core 102 and the n-type silicon core 103 is a square having a side of 500 nm. Further, the silicon core may have a width of 500 μm and a height of 500 μm. In this case, each cross section of the p-type silicon core 102 and the n-type silicon core 103 is a rectangle having a width of 250 nm and a height of 500 nm.

  The lower cladding layer 101 and each silicon core formed thereon can be formed, for example, by processing a known SOI (Silicon on Insulator) substrate. The buried insulating layer of the SOI substrate is used as the lower cladding layer 101, and the single crystal silicon layer thereon is processed by a known photolithography technique and etching technique, and selectively ion-implanted, whereby the p-type silicon core 102 and n A shaped silicon core 103 can be formed. Alternatively, by selectively ion-implanting to form a p-type region and an n-type region, a stripe-shaped pattern can be formed around the pn junction surface, thereby forming the p-type silicon core 102 and An n-type silicon core 103 can be formed.

  Further, on both sides of the p-type silicon core 102 and the n-type silicon core 103, a side cladding layer (first layer) made of a conductive material having a lower refractive index than the silicon core, such as a zinc oxide compound or an indium oxide compound. 1 clad layer) 104a, side clad layer (second clad layer) 104b, and an upper clad layer 105 covering them. Therefore, the side clad layer 104a and the side clad layer 104b are sandwiched between the lower clad layer 101 and the upper clad layer 105, and are opposed to each other with the silicon core composed of the p-type silicon core 102 and the n-type silicon core 103 interposed therebetween. ing.

  The lower cladding layer 101 and the upper cladding layer 105 may be made of a dielectric material having a lower refractive index than the silicon core, such as a silicon oxide compound, a silicon nitride compound, an epoxy polymer material, and a polyimide polymer material. Good. An optical waveguide is constituted by the p-type silicon core 102, the n-type silicon core 103, and the clads covering the lower, side, and upper portions thereof.

  In addition, contact plugs 106 and 107 penetrating the upper cladding layer 105 are connected to the side cladding layers 104a and 104b. In addition, the side clad layers 104 a and 104 b are connected to electrodes 108 and 109 formed on the upper clad layer 105 via contact plugs 106 and 107. A power source 110 is connected to the electrodes 108 and 109, and a bias voltage can be applied between them. Note that an ammeter 111 is connected to the power source 110 in series.

  According to the photodetector of FIG. 1 configured as described above, carriers (electron-hole pairs) generated by two-photon absorption (multiphoton absorption) inside the p-type silicon core 102 and the n-type silicon core 103 are converted into current. It is detected as a current by the total 111. Therefore, according to the photodetector of FIG. 1, it is possible to detect light guided through a waveguide formed by the p-type silicon core 102 and the n-type silicon core 103.

  FIG. 2 is a cross-sectional view schematically showing a configuration example of a photodetector array using the photodetector shown in FIG. A plurality of photodetectors 200 are arranged on a common lower cladding layer 201, and each photodetector 200 is insulated and separated by an insulating layer 220. The insulating layer 220 may be made of an insulating material such as a silicon oxide compound, a silicon nitride compound, an epoxy polymer compound, and a polyimide polymer compound. The insulating layer 220 may be composed of an air layer. In other words, the photodetectors 200 may be arranged on the lower clad layer 201 at a predetermined interval. When light with a wavelength of 1.1 to 2.2 μm is targeted, the gap between the photodetectors 200, that is, the thickness of the insulating layer 220 may be about 2 μm.

Here, the above-described two-photon absorption will be described. FIG. 3 shows a measurement system 300 for studying two-photon absorption (multiphoton absorption), which is composed of a silicon core and a lower refractive index cladding. Light having a wavelength of 1.1 μm <λ ₁ <2.2 μm modulated into a bit pattern by a pattern generator 302 and an optical modulator 303 is input to the optical waveguide 301 and measured by an O / E sampling oscilloscope 304.

  Since the light incident on the optical waveguide 301 has a wavelength longer than the band gap of silicon, when the light intensity is low, the light is transmitted (guided) through the optical waveguide 301 and output (emitted). The silicon core optical waveguide 301 can guide light even if the diameter of the core is 500 nm or less as long as the light has a wavelength of 1.1 to 2.2 μm. The light intensity of 1.1 to 2.2 is remarkably increased in the core. In this structure, the intensity of light guided through the optical waveguide 301 is increased, and when this intensity exceeds a predetermined value, two-photon absorption occurs, carriers (electron-hole pairs) are generated, and light absorption occurs. It should be noted that light having a higher light intensity causes three-photon absorption, four-photon absorption, and multiphoton absorption in the optical waveguide 301.

  In addition, when electron-hole pairs generated by two-photon absorption recombine, light having twice the energy of the control light is emitted, but the energy is larger than the band gap of silicon forming the core of the optical waveguide 301. Since it is large, the light emitted by recombination cannot propagate through the optical waveguide 301. Therefore, the state of two-photon absorption in the optical waveguide 301 can be confirmed by measuring the state of the light extracted after being guided through the optical waveguide 305.

  FIG. 4 is a characteristic diagram showing a waveform of light incident on the optical waveguide 301. As shown in FIG. 4, light modulated into a bit pattern is incident on the optical waveguide 301. FIG. 5 is a characteristic diagram showing the waveform of light obtained as a result of measuring the light emitted from the optical waveguide 301 with the O / E sampling oscilloscope 304. FIG. 6 is a characteristic diagram in which the values of B / A in FIG. 5 are plotted when the peak intensity of the bit pattern light incident on the optical waveguide 301 is changed.

  As can be seen from FIG. 6, the peak intensity of light incident on the optical waveguide 301 and the reciprocal of the transmittance of the input bit pattern light in the optical waveguide 301 are in a proportional relationship, and the attenuation of light shown in FIG. It shows that it is two-photon absorption in the optical waveguide 301 (reference: JHBechtel and WLSmith, “Two-photon absorption in semiconductors with picosecond laser pulses”, PHYSICAL REVIEW B, Vo.13, No.8, pp3515- 3522, 15th APRIL 1976.).

  Here, a pn junction is provided by providing a pn junction in the silicon core of the optical waveguide 301, applying a reverse bias to the pn junction, and connecting electrodes to the p-type region and the n-type region of the core, respectively. Electron hole pairs (carriers) generated in the core can be taken out as electrical signals from the electrodes. That is, according to the photodetector shown in FIG. 1 in which a pn junction is provided in a core made of silicon, two-photon absorption generated in the core can be extracted as an electric signal. As described above, the photodetector shown in FIG. 1 can detect light having a light intensity equal to or greater than a predetermined value.

  By the way, since the photodetector shown in FIG. 1 is a waveguide type, when an electrode for extracting carriers from a pn junction provided in the core is made of metal, the metal exists in the vicinity of the core through which light propagates. Conductor loss is large and not efficient. For this reason, as described above, the side cladding layers 104a and 104b on both sides of the p-type silicon core 102 and the n-type silicon core 103 have a lower refractive index than silicon cores such as zinc oxide compounds and indium oxide compounds. It is made of a conductive material, and these are used as lead electrodes (wirings) for connecting to the electrodes 108 and 109. Since these materials have a smaller refractive index than silicon, they function not only as wiring but also as cladding.

  The photodetector shown in FIG. 1 described above can be easily miniaturized and is of an optical waveguide type, so that it can be easily connected to a silicon nano-optical waveguide or the like. Therefore, the use of the photodetector shown in FIG. 1 facilitates miniaturization of the optical integrated circuit. Further, in the case of the photodetector shown in FIG. 1, even if a plurality of the photodetectors are arranged to form an array connection configuration as shown in FIG. 2, the entire device is not increased and miniaturization is easy.

[Embodiment 2]
Next, another photodetector in the embodiment of the present invention will be described. FIG. 7 is a perspective view schematically showing a configuration example of another photodetector in the present invention.
This photodetector includes a p-type silicon core 102 and an n-type silicon core 103 disposed adjacent to each other on the lower clad layer 101, similarly to the photodetector shown in FIG. Further, side clad layers 104 a and 104 b are provided on both sides of the p-type silicon core 102 and the n-type silicon core 103.

  The photodetector shown in FIG. 7 includes an upper clad layer 705 that covers the p-type silicon core 102 and the n-type silicon core 103 and extends to a part of the side clad layers 104a and 104b, and includes the side clad layer 104a. 104b are exposed. The upper clad layer 705 only needs to cover at least the p-type silicon core 102 and the n-type silicon core 103 to such an extent that a waveguide is formed by the p-type silicon core 102 and the n-type silicon core 103. The upper clad layer 705 is disposed so that the center of the waveguide in the waveguide direction is at the same position as the center of the core composed of the p-type silicon core 102 and the n-type silicon core 103.

  The width of the upper cladding layer 705 in the direction perpendicular to the waveguide direction may be set as appropriate depending on the combination of the wavelength of light guided through the core and the material constituting the cladding layer. For example, the wavelength of light guided through the core is 1.1 to 2.2 μm, and the material constituting the upper cladding layer 705 is the silicon oxide compound, silicon nitride compound, epoxy polymer material, and In the case of a polyimide polymer material or the like, the width of the upper clad layer 705 may be 2 μm or more.

  In the photodetector of FIG. 7 configured as described above, a power source 110 is connected to the side cladding layer 104a and the side cladding layer 104b, and a bias voltage can be applied between them. Note that an ammeter 111 is connected to the power source 110 in series. Also in the photodetector of FIG. 7, it is possible to detect light guided through a waveguide formed by the p-type silicon core 102, the p-type silicon core 102, and the n-type silicon core 103. Note that an electrode pad made of metal may be provided on each of the side clad layer 104a and the side clad layer 104b, and the power source 110 may be connected thereto.

  By the way, even the photodetector shown in FIG. 7 can be configured as a photodetector array as shown in FIG. In this case, a plurality of photodetectors 800 are arranged on a common lower cladding layer 801, and each photodetector 800 is insulated and separated by an insulating layer 820. The insulating layer 820 may be formed of an insulating material such as a silicon oxide compound, a silicon nitride compound, an epoxy polymer compound, and a polyimide polymer compound. Further, the insulating layer 820 may be composed of an air layer. In other words, the photodetectors 800 may be arranged on the lower clad layer 801 at a predetermined interval. When light having a wavelength of 1.1 to 2.2 μm is targeted, the gap between the photodetectors 800, that is, the thickness of the insulating layer 820 may be about 2 μm.

[Embodiment 3]
Next, another photodetector in the embodiment of the present invention will be described. FIG. 9 is a perspective view schematically showing a configuration example of another photodetector in the present invention.
This photodetector includes a p-type silicon core 902 on a lower clad layer (first clad layer) 901 made of a conductive material having a lower refractive index than that of a silicon core such as a zinc oxide compound or an indium oxide compound. And an n-type silicon core 903 laminated thereon. The p-type silicon core 902 and the n-type silicon core 903 form a pn junction surface parallel to the main surface of the lower cladding layer 901.

  Further, side clad layers 904 are provided on both sides of the stacked p-type silicon core 902 and n-type silicon core 903. The side cladding layer 904 may be made of a dielectric material having a lower refractive index than the silicon core, such as a silicon oxide compound, a silicon nitride compound, an epoxy polymer material, and a polyimide polymer material. In addition, an upper clad layer (second clad layer) 905 covering the upper surface of the n-type silicon core 903 and the upper surface of the side clad layer 904 is provided. Accordingly, the side clad layer 904 is disposed so as to face the silicon core composed of the p-type silicon core 902 and the n-type silicon core 903 and is sandwiched between the lower clad layer 901 and the upper clad layer 905.

  Similarly to the lower clad layer 901, the upper clad layer 905 only needs to be made of a conductive material having a lower refractive index than a silicon core such as a zinc oxide compound or an indium oxide compound. An optical waveguide is constituted by the p-type silicon core 902, the n-type silicon core 903, and the clads covering the lower, side, and upper portions thereof.

  In the photodetector shown in FIG. 9, a power source is connected to the lower cladding layer 901 and the upper cladding layer 905, a reverse bias voltage is applied between them, and an ammeter connected in series to the power source is provided. Carriers generated by two-photon absorption (multi-photon absorption) inside the p-type silicon core 902 and the n-type silicon core 903 are detected as current by an ammeter. Therefore, even with the photodetector shown in FIG. 9, it is possible to detect the light guided through the waveguide formed by the p-type silicon core 902 and the n-type silicon core 903.

  As is clear from the configuration of the photodetector shown in FIGS. 1 and 7 and the configuration of the photodetector shown in FIG. 9, a p-type core and n are formed so that a pn junction surface extends in the waveguide direction. It is important that the cross section of the silicon core made of these has a dimension in at least one direction of 500 nm or less, a bias voltage is applied to them, and the flowing current can be measured. is there. For applying voltage and measuring current, a p-type clad having conductivity is provided in contact with the p-type core, and an n-type clad having conductivity is provided in contact with the n-type core. The clad for the shape and the clad for the n-type are insulatively separated, and each clad can be used as a wiring (extraction electrode). Further, by adopting this configuration, the conductor loss of the waveguide made of the core can be prevented and the efficiency is improved.

In the photodetector shown in FIG. 9, it is not necessary to cover the entire side cladding layer 904 with the upper cladding layer 905. An upper cladding layer 905 having a predetermined width that is appropriately set according to the wavelength of light to be guided may be provided centering on the n-type silicon core 903. Further, the photodetector shown in FIG. 9 is not limited to the configuration in which the n-type silicon core is disposed on the p-type silicon core, and it goes without saying that the configuration may be reversed.
In the photodetector shown in FIG. 9, electrode pads made of metal may be provided in the lower clad layer 901 and the upper clad layer 905, and a power source may be connected thereto.

  By the way, even the photodetector shown in FIG. 9 can have a configuration of a photodetector array as shown in FIG. In this case, a plurality of photodetectors 1000 are arranged on a common lower cladding layer 1001, and each photodetector 1000 is insulated and separated by an insulating layer 1020. In this case, the side cladding layers 904 disposed between the cores of the adjacent photodetectors 1000 can be used in common.

  Note that the insulating layer 1020 may be formed of an insulating material such as a silicon oxide compound, a silicon nitride compound, an epoxy polymer compound, and a polyimide polymer compound. Further, the insulating layer 820 may be composed of an air layer. In other words, the photodetectors 800 may be arranged on the lower clad layer 801 at a predetermined interval. When light with a wavelength of 1.1 to 2.2 μm is targeted, the gap between the photodetectors 1000, that is, the thickness of the insulating layer 1020 may be about 2 μm.

Next, a configuration in which the above-described photodetector and optical waveguide are integrated will be described.
FIG. 11 is a perspective view schematically showing a state in which an optical waveguide is connected in series to the photodetector shown in FIG. The photodetector 100 includes a p-type silicon core 102 and an n-type silicon core 103 disposed adjacent to each other on the lower cladding layer 101. Further, side clad layers 104 a and 104 b are provided on both sides of the p-type silicon core 102 and the n-type silicon core 103, and an upper clad layer 105 covering these is provided.

  In addition, contact plugs 106 and 107 penetrating the upper cladding layer 105 are connected to the side cladding layers 104a and 104b. In addition, the side clad layers 104 a and 104 b are connected to electrodes 108 and 109 formed on the upper clad layer 105 via contact plugs 106 and 107. A power source 110 is connected to the electrodes 108 and 109, and a bias voltage can be applied between them. Note that an ammeter 111 is connected to the power source 110 in series. These are the same as the configuration shown in FIG.

  In the optical integrated circuit shown in FIG. 11, a waveguide 150 is connected to the photodetector 100 described above. The waveguide 150 includes a silicon core 151 connected to the p-type silicon core 102 and the n-type silicon core 103. The lower, upper, and side claddings of the silicon core 151 are common to the lower cladding layer 101, the side cladding layers 104a and 104b, and the upper cladding layer 105. Note that, in the region of the waveguide 150, a silicon core such as a silicon oxide compound, a silicon nitride compound, an epoxy polymer material, and a polyimide polymer material is formed on the side cladding layer in the same manner as the upper cladding layer 105. A dielectric material having a lower refractive index may be used.

  FIG. 11 shows an example of an integrated circuit in which the waveguide 150 is connected to the photodetector 100. However, the present invention is not limited to this, and as shown in the plan view of FIG. A configuration in which the waveguides 150 are connected in series may be employed. 11 shows an example in which the photodetectors shown in FIG. 1 are integrated, the present invention is not limited to this, and the photodetectors shown in FIGS. 7 and 9 may be integrated.

  Moreover, as shown in FIGS. 13 and 14, a serial optical circuit of the photodetector 100 and the optical waveguide 150 may be arranged in parallel. In this case, an insulating layer 230 is provided between adjacent optical circuits. The insulating layer 230 is provided so as to insulate and isolate the photodetectors 100 adjacent to each other in the direction perpendicular to the extending direction of the optical circuit. In the plan view of FIG. 14, the insulating layer 230 is omitted.

It is a perspective view which shows typically the structural example of the photodetector in embodiment of this invention. It is sectional drawing which shows typically the structural example of the photodetector array using the photodetector shown in FIG. It is a block diagram which shows the structural example of the measurement system for examining two-photon absorption (multiphoton absorption). FIG. 4 is a characteristic diagram illustrating a waveform of light input to the measurement system illustrated in FIG. 3. FIG. 4 is a characteristic diagram showing a waveform of light obtained as a result of measuring light output from the measurement system shown in FIG. 3 with an O / E sampling oscilloscope 304; FIG. 6 is a characteristic diagram in which the values of B / A in FIG. 5 are plotted when the input peak intensity of light input to the measurement system shown in FIG. 3 is changed. It is a perspective view which shows typically the structural example of the other photodetector in this invention. It is sectional drawing which shows typically the structural example of the photodetector array using the photodetector shown in FIG. It is a perspective view which shows typically the structural example of the other photodetector in this invention. It is sectional drawing which shows typically the structural example of the photodetector array using the photodetector shown in FIG. It is a perspective view which shows typically the state by which the optical waveguide was connected in series with the photodetector shown in FIG. 4 is a plan view showing a configuration in which a plurality of photodetectors 100 are connected in series by a waveguide 150. FIG. FIG. 5 is a perspective view showing a configuration in which serial optical circuits of a photodetector 100 and an optical waveguide 150 are arranged in parallel. 3 is a plan view showing a configuration in which serial optical circuits of a photodetector 100 and an optical waveguide 150 are arranged in parallel. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 ... Lower clad layer, 102 ... p-type silicon core, 103 ... n-type silicon core, 104a, 104b ... Side clad layer, 105 ... Upper clad layer, 106, 107 ... Contact plug, 108, 109 ... Electrode, 110 ... Power supply, 111 ... ammeter.

Claims (5)

A core made of silicon having a p-type region and an n-type region formed so that a pn junction surface extends in the waveguide direction and having a dimension in at least one direction of a cross section of 500 nm or less;
A power supply for applying a predetermined bias voltage between the p-type region and the n-type region of the core;
An ammeter for measuring a current flowing between the p-type region and the n-type region of the core;
A photodetector having at least a cladding disposed around the core and having a refractive index lower than that of silicon. The photodetector of claim 1.
The cladding is
A first cladding layer made of a conductive material in contact with the p-type region of the core;
A second cladding layer made of a conductive material in contact with the n-type region of the core;
The third clad layer and the fourth clad layer are made of an insulating material disposed so as to sandwich the core so as to insulate and separate the first clad layer and the second clad layer. To light detector. The photodetector according to claim 2.
The first clad layer and the second clad layer are sandwiched between the third clad layer and the fourth clad layer, and are arranged to face each other with the core therebetween. The photodetector according to claim 2.
The photodetector is characterized in that the third clad layer and the fourth clad layer are sandwiched between the first clad layer and the second clad layer and are opposed to each other across the core. In the photodetector of any one of Claims 2-4,
The first clad layer and the second clad layer are made of any material selected from a zinc oxide compound or an indium oxide compound. The photodetector.

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