Abstract: A purpose is to provide a semiconductor optical device having good characteristics to be formed on a semi-insulating InP substrate. Firstly, a semi-insulating substrate including a Ru—InP layer on a conductive substrate is used. Secondly, a semi-insulating substrate including a Ru—InP layer on a Ru—InP substrate or an Fe—InP substrate is used and semiconductor layers of an n-type semiconductor layer, a quantum-well layer, and a p-type semiconductor layer are stacked in this order.

Abstract: A photodetector/imaging device comprises a layer of photoconductive material converting incident electromagnetic radiation into electrical charges, the layer of photoconductive material being capable of avalanche multiplication when an electric field of sufficient magnitude is applied thereacross; a readout layer detecting the electrical charge; and at least one interface layer between the layer of photoconductive material and the readout layer, the interface layer coupling electrical charge to or from the layer of photoconductive material and being configured to inhibit uncontrolled rises in current in the photoconductive material during avalanche multiplication.

Abstract: A dual-pixel full color complementary metal oxide semiconductor (CMOS) imager is provided, along with an associated fabrication process. Two stand-alone pixels are used for three-color detection. The first pixel is a single photodiode, and the second pixel has two photodiodes built in a stacked structure. The two photodiode stack includes an n doped substrate, a bottom photodiode, and a top photodiode. The bottom photodiode has a bottom p doped layer overlying the substrate and a bottom n doped layer cathode overlying the bottom p doped layer. The top photodiode has a top p doped layer overlying the bottom n doped layer and a top n doped layer cathode overlying the top p doped layer. The single photodiode includes the n doped substrate, a p doped layer overlying the substrate, and an n doped layer cathode overlying the p doped layer.

Abstract: The invention relates to high-efficient light-recording detectors and can be used for nuclear and laser engineering, and in technical and medical tomography etc. The inventive silicon photoelectric multiplier (variant 1) comprising a p++ type conductivity substrate whose dope additive concentration ranges from 1018 to 1020 cm ?3 and which consists of cells, each of which comprises a p? type conductivity epitaxial layer whose dope additive concentration is gradually changeable from 1018 to 1014 cm?3 and which is grown on the substrate, a p? type conductivity layer whose dope additive concentration ranges from 1015 to 1017 cm?3 and a n+ type conductivity layer whose dope additive concentration ranges from 1018 to 1020 cm?3, wherein a polysilicon resistor connecting the n+ type conductivity layer with a feed bar is arranged in each cell on a silicon oxide layer and separating elements are disposed between the cells.

Abstract: A solid-state imaging device includes: an avalanche photodiode having a structure including an n+ region, a p+ region, and an avalanche region interposed between the n+ region and the p+ region, all of which are formed to extend in a thickness direction of a semiconductor base; and a pixel repeatedly having the structure of the avalanche photodiode.

Abstract: A single-photon avalanche detector is disclosed that is operable at wavelengths greater than 1000 nm and at operating speeds greater than 10 MHz. The single-photon avalanche detector comprises a thin-film resistor and avalanche photodiode that are monolithically integrated such that little or no additional capacitance is associated with the addition of the resistor.

Abstract: A pixel for an imager is disclosed that includes at least one electron multiplication (EM) gain stage configured in a loop and electrically coupled to a charge collection region and a charge readout region, the charge collection region being configured to generate a charge packet, the EM gain stage being configured to amplify the charge packet by impact ionization and to circulate the charge packet a predetermined number of times in one direction around the loop, the charge readout region being configured to receive the amplified charge packet and convert the amplified charge to a measurable signal. The at least one EM gain stage, the charge collection region, and the charge readout region can be formed monolithically in an integrated circuit. The pixel can be manufactured using a CMOS process. The pixel can further include a second EM gain stage formed in the integrated circuit to increase the amount of amplification around the loop.

Abstract: An avalanche photodetector is disclosed. An apparatus according to aspects of the present invention includes a semiconductor substrate layer including a first type of semiconductor material. The apparatus also includes a multiplication layer including the first type of semiconductor material disposed proximate to the semiconductor substrate layer. The apparatus also includes an absorption layer having a second type of semiconductor material disposed proximate to the multiplication layer such that the multiplication layer is disposed between the absorption layer and the semiconductor substrate layer. The absorption layer is optically coupled to receive and absorb an optical beam. The apparatus also includes an n+ doped region of the first type of semiconductor material defined at a surface of the multiplication layer opposite the absorption layer.

Abstract: An embodiment of a Geiger-mode avalanche photodiode includes a body of semiconductor material having a first conductivity type, a first surface and a second surface; a trench extending through the body from the first surface and surrounding an active region; a lateral-isolation region within the trench, formed by a conductive region and an insulating region of dielectric material, the insulating region surrounding the conductive region; an anode region having a second conductivity type, extending within the active region and facing the first surface. The active region forms a cathode region extending between the anode region and the second surface, and defines a quenching resistor. The photodiode has a contact region of conductive material, overlying the first surface and in contact with the conductive region for connection thereof to a circuit biasing the conductive region, thereby a depletion region is formed in the active region around the insulating region.

Abstract: A semiconductor device is disclosed. The semiconductor device comprises, a first region of a first conductivity type, a second region of a second conductivity type disposed adjacent to the first region to form a p-n junction structure, a resistance modification region of the second conductivity type, and a field response modification region of the second conductivity type disposed between the resistance modification region and the second region, wherein the field response modification region comprises a varying dopant concentration distribution along a thickness direction of the field response modification region.

Abstract: A semiconductor device includes a semiconductor substrate, a photon avalanche detector in the semiconductor substrate. The photon avalanche detector includes an anode of a first conductivity type and a cathode of a second conductivity type. A guard ring is in the semiconductor substrate and at least partially surrounds the photon avalanche detector. A passivation layer of the first conductivity type is in contact with the guard ring to reduce an electric field at an edge of the photon avalanche detector.

Abstract: An avalanche photodiode comprises: a substrate; a semiconductor layer of a first conductivity type on the substrate; and an avalanche multiplication layer, a light absorption layer, and a window layer which are sequentially formed on the semiconductor layer, wherein apart of the window layer is a region of a second conductivity type, and the light absorption layer includes a first light absorption layer, and a second light absorption layer which has higher electric conductivity than electric conductivity of the first light absorption layer.

Abstract: A single-photon avalanche detector is disclosed that is operable at wavelengths greater than 1000 nm and at operating speeds greater than 10 MHz. The single-photon avalanche detector comprises a thin-film resistor and avalanche photodiode that are monolithically integrated such that little or no additional capacitance is associated with the addition of the resistor.

Abstract: The invention relates to an overvoltage protection apparatus having a semiconductor substrate, a first doping region in order to provide a protection diode, and a second doping region in order to provide a protection resistance, with the second doping region being immediately adjacent to the first doping region.

Abstract: Methods of fabricating semiconductor devices using electrode-less wet-etching techniques to reduce defect densities on etched group III-nitride semiconductor surfaces are described herein. The methods generally involve contacting an etched surface of a component of a semiconductor device with a solution comprising a metal hydroxide and an oxidizing agent effective to reduce a roughness of the etched surface, wherein the etched surface is formed from a composition comprising a nitride of a group III element. Improved semiconductor devices are also disclosed.

Abstract: Photonic power switch and method of controlling current flow in the photonic power switch, the photonic power switch comprising an avalanche photo diode installed on a switch element, the switch element comprising a carrier donor layer and a channel layer. Photons are injected in the avalanche photo diode for generating electrical charge carriers by photoeffect, and the generated charge carriers are accelerated the by an electric field so as to produce an avalanche effect and are injected from the avalanche photo diode into the carrier donor layer of the switch element. A conduction layer built between the donor layer and the channel layer of the switch element is modulated, thereby modulating a current flow between a drain and a source of the power switch through said conduction layer.

Abstract: Disclosed herein is a solid-state imaging element which includes a plurality of drive signal inputs, a plurality of bus lines, and a plurality of vertical transfer register electrodes. In the solid-state imaging element, a charge accumulated in light-receiving elements in a pixel region is vertically transferred by the drive signals input to the electrodes. Each of the electrodes has a contact part connected to the second contact and having a width smaller than a width of the electrodes in the pixel region, and a blank region is formed between predetermined adjacent two of the contact parts so that a width of the blank region is larger than a distance between respective two of the contact parts other than the predetermined adjacent two of the contact parts. The first contact is disposed on the blank region.

Abstract: A single-photon detector is disclosed that provides reduced afterpulsing without some of the disadvantages for doing so in the prior art. An embodiment of the present invention provides a stimulus pulse to the active area of an avalanche photodetector to stimulate charges that are trapped in energy trap states to detrap. In some embodiments of the present invention, the stimulus pulse is a thermal pulse.

Abstract: Techniques and apparatus for using single photon avalanche diode (SPAD) devices in various applications.

Abstract: A photoelectronic device and an avalanche self-quenching process for a photoelectronic device are described. The photoelectronic device comprises a nanoscale semiconductor multiplication region and a nanoscale doped semiconductor quenching structure including a depletion region and an undepletion region. The photoelectronic device can act as a single photon detector or a single carrier multiplier. The avalanche self-quenching process allows electrical field reduction in the multiplication region by movement of the multiplication carriers, thus quenching the avalanche.

Abstract: A single-photon detector is disclosed that provides reduced afterpulsing without some of the disadvantages for doing so in the prior art. An embodiment of the present invention provides a stimulus pulse to the active area of an avalanche photodetector to stimulate charges that are trapped in energy trap states to detrap. In some embodiments of the present invention, the stimulus pulse is a thermal pulse.

Abstract: A photodiode with an improved electrostatic damage threshold is disclosed. A Zener or an avalanche diode is connected in parallel to a photodiode. Both diodes are integrated into the same photodiode housing. The diodes can be mounted on a common header or onto each other. An avalanche photodiode and an avalanche diode can be fabricated on a common semiconductor substrate. A regular p-n diode connected in series, cathode-to-cathode or anode-to-anode, to a Zener diode, forms a protection circuit which, when connected in parallel to a photodiode, provides a smaller electrical capacity increase as compared to a simpler circuit consisting just of a Zener or an avalanche diode.

Abstract: An optical semiconductor device includes a light-receiving element on a semiconductor substrate of a first conductivity type, the light-receiving element including a light-receiving portion for converting incident light to an electrical current signal and performing a current amplification. The light-receiving portion includes: a semiconductor layer formed on the semiconductor substrate and having an impurity concentration substantially equal to or less than that of the semiconductor substrate; a first semiconductor region of a second conductivity type formed on the semiconductor layer and having an impurity concentration higher than that of the semiconductor layer; and a second semiconductor region of the first conductivity type selectively formed between the semiconductor substrate and the semiconductor layer and having an impurity concentration higher than those of the semiconductor substrate and the semiconductor layer.

Abstract: A photodiode array 1 has a plurality of photodetector channels 10 which are formed on an n-type substrate 2 having an n-type semiconductor layer 12, with a light to be detected being incident to the plurality of photodetector channels 10. The photodiode array 1 comprises: a p?-type semiconductor layer 13 formed on the n-type semiconductor layer 12 of the substrate 2; resistors 4 each of which is provided to each of the photodetector channels 10 and is connected to a signal conductor 3 at one end thereof; and an n-type separating part 20 formed between the plurality of photodetector channels 10. The p?-type semiconductor layer 13 forms a pn junction at the interface between the substrate 2, and comprises a plurality of multiplication regions AM for avalanche multiplication of carriers produced by the incidence of the light to be detected so that each of the multiplication regions corresponds to each of the photodetector channels.

Abstract: Avalanche photodiodes are provided, wherein the APDs provide both high optical coupling efficiency and low dark count rate. The APDs are formed such that their cap layer has an active region of sufficient width to enable high optical coupling efficiency but the APD still exhibits a low dark count rate. These cap layers have a device area with an active region and an edge region, wherein the size of the active region is substantially matched to the mode-field diameter of an optical beam, and wherein the size of the edge region is made small so as to reduce the number of defects included. These APD designs maintain a substantially uniform gain and breakdown voltage, as necessary for practical use.

Abstract: An improved semiconductor apparatus that comprises an elongated structure that extends into the substrate. The apparatus comprises a collection contact, a resistive path, a bias connection that creates along the length of the elongated structure, an electric field component that drives signal charge carriers in a direction perpendicular to the elongated structure, and a second bias that generates a current flow that creates within the substrate a constant electric field component to drive signal charge carriers towards the collection contact on the first surface.

Abstract: An optical receiver is disclosed, in which no additional photodiode to monitor the optical input level and no temperature control unit are necessary. The receiver of the invention provides an avalanche photodiode (APD) to receiver the first optical signal with the first wavelength and a PIN-PD to receive the second optical signal with the second wavelength. The optical input level for the APD is indirectly determined through the photocurrent generated by the PIN-PD and the bias voltage for the APD is so adjusted that the APD shows an optimum multiplication factor for the optical input level.

Abstract: An embodiment of an array of Geiger-mode avalanche photodiodes, wherein each photodiode is formed by a body of semiconductor material, having a first conductivity type, housing a first cathode region, of the second conductivity type, and facing a surface of the body, an anode region, having the first conductivity type and a higher doping level than the body, extending inside the body, and facing the surface laterally to the first cathode region and at a distance therefrom, and an insulation region extending through the body and insulating an active area from the rest of the body, the active area housing the first cathode region and the anode region. The insulation region is formed by a mirror region of metal material, a channel-stopper region having the second conductivity type, surrounding the mirror region, and a coating region, of dielectric material, arranged between the mirror region and the channel-stopper region.

Abstract: An embodiment of array of Geiger-mode avalanche photodiodes, wherein each photodiode is formed by a body of semiconductor material, having a first conductivity type and housing an anode region, of a second conductivity type, facing a top surface of the body, a cathode-contact region, having the first conductivity type and a higher doping level than the body, facing a bottom surface of the body, an insulation region extending through the body and insulating an active area from the rest of the body, the active area housing the anode region and the cathode-contact region. The insulation region is formed by a first mirror region of polycrystalline silicon, a second mirror region of metal material, and a channel-stopper region of dielectric material, surrounding the first and second mirror regions.

Abstract: In a semiconductor photo-detecting element (an avalanche photodiode), a high-sensitivity element is obtained by incorporating a multiplication layer having high-performance multiplication characteristics. By using a structure which reduces an electric field applied to an etching stopper layer, it is possible to use a multiplication layer having higher-performance multiplication characteristics (a multiplication layer which performs multiplication with a high electric field). The first method to realize this is to use a conductivity type multiplication layer. The second method is to use a structure in which a field buffer layer of the second conductivity type is incorporated. As a result of the use of these methods, a structure which applies an electric field lower than the multiplier electrical field to the etching stopper layer is obtained.

Abstract: A complementary metal-oxide semiconductor (CMOS)-based planar type avalanche photo diode (APD) using a silicon epitaxial layer and a method of manufacturing the APD, the photo diode including: a substrate; a well layer of a first conductivity type formed in the substrate; an avalanche embedded junction formed in the well layer of the first conductivity type by low energy ion implantation; the silicon epitaxial layer formed in the avalanche embedded junction; a doping area of a second conductivity type opposite to the first conductive type, formed from a portion of a surface of the well layer of the first conductivity type in the avalanche embedded junction and forming a p-n junction; positive and negative electrodes formed on the doping area of the second conductivity type and the well layer of the first conductivity type separated from the doping area of the second conductivity type, respectively; and an oxide layer formed on an overall surface excluding a window where the positive and negative electrodes ar

Abstract: The present invention proposes a real time active imaging method that is accurate and simple, and able to give distance information concerning the observed objects. More specifically, the invention relates to a method of detecting a light pulse reflected on an object (O1, O2, O3), comprising the following steps: c) emitting a light pulse of known intensity and duration towards the object (O1, O2, O3), then d) detecting a reflection signal (P1, P2, P3, P4, P5) of the light pulse on the object (O1, O2, O3) during a determined integration time (?t), with at least one gain sensor able to amplify the reflection signal, wherein, on detection during the integration time (?t), the gain of the sensor or sensors is varied in a controlled manner in order to know the gain at each instant of the integration time (?t), and which also comprises the following step: i) determining the precise instant of return of the reflection signal by evaluating the amplification gain of the reflection signal.

Abstract: A PIN photodiode having a substrate, a first type electrode layer disposed on the substrate, a first layer of intrinsic material disposed over a portion of the first-type electrode layer, a first type window layer disposed over said intrinsic layer. An island shaped region of intrinsic material is disposed over the window layer and a dielectric layer disposed over the island region and at least the peripheral portion of said island shaped region whereby an opening is formed in the island shaped region. A dopant is diffused through the opening so as to form a PN junction that extends into the first layer of intrinsic material.

Abstract: The present invention provides a photodiode array which can secure a sufficient aperture ratio with respect to light to be detected while restraining crosstalk between photodetecting channels even during operation in Geiger mode. In a photodiode array 1, resistors 42 and wirings 43 to be electrically connected to avalanche multipliers 6, respectively, are collectively formed on the upper surface side of a semiconductor substrate 2. Therefore, by setting the lower surface side of the semiconductor substrate 2 as a light-incident side, a sufficient aperture ratio can be secured while restraining crosstalk between photodetecting channels 10 by separators 5. Furthermore, on the lower surface side of the semiconductor substrate 2, accumulation layers 7 are formed, so that high quantum efficiency in each photodetecting channel 10 is secured and the effective aperture ratio is improved.

Abstract: An image sensor includes a pixel having a protection circuit connected to a charge multiplying photoconversion layer. The protection circuit prevents the pixel circuit from breaking down when the voltage in the pixel circuit reaches the operating voltage applied to the charge multiplying photoconversion layer in response to the image sensor being exposed to a strong light. The protection circuit causes additional voltage entering the pixel circuit from the charge multiplying photoconversion layer over a predetermined threshold voltage level to be dissipated from the storage node and any downstream components.

Abstract: A method of fabricating light-sensing devices including photodiodes monolithically integrated with CMOS devices. Several types of photodiode devices (PIN, HIP) are expitaxially grown in one single step on active areas implanted in a common semiconductor substrate, the active areas having defined polarities. The expitaxially grown layers for the photodiode devices may be either undoped or in-situ doped with profiles suitable for their respective operation. With appropriate choice of substrate materials, device layers and heterojunction engineering and process architecture, it is possible to fabricate silicon-based and germanium-based multi-spectral sensors that can deliver pixel density and cost of fabrication comparable to the state of the art CCDs and CMOS image sensors. The method can be implemented with epitaxially deposited films on the following substrates: Silicon Bulk, Thick-Film and Thin-Film Silicon-On-Insulator (SOI), Germanium Bulk, Thick-Film and Thin-Film Geranium-On-Insulator (GeOI).

Abstract: A radiation detector (46) includes a semiconductor layer(s) (12) formed on a substrate (14) and a scintillator (30) formed on the semiconductor layer(s) (12). The semiconductor layer(s) (12) includes an n?doped region (16) disposed adjacent to the substrate (14), and a p?doped region (18) disposed adjacent to the n?doped region (16). A trench (20) is formed within the semiconductor layer(s) (12) and around the p?doped region (18) and is filled with a material (22) that reduces pn junction curvature at the edges of the pn junction, which reduces breakdown at the edges. The scintillator (30) is disposed over and optically coupled to the p?doped regions (18). The radiation detector (46) further includes at least one conductive electrode (24) that electrically contacts the n?doped region.

Abstract: Systems and methods for a structure for a power distribution network intended to distribute power from a PCB to a semiconductor device on a package. These improved power distribution networks may reduce current crowding in the BGA balls of a package and may serve to more equitably distribute current through the BGA balls of the package through increasing the impedance of the package or decreasing the impedance of the PCB to which the package is coupled. These systems and methods may increase the impedance of the package through various arrangements of the coupling between BGA balls and planes of the package. By the same token, these systems and methods may decrease the impedance of the PCB coupled to the package by arrangement of the coupling between the PCB and the BGA balls of the package.

Abstract: An avalanche photodiode detector is provided. The avalanche photodiode detector comprises an absorber region having an absorption layer for receiving incident photons and generating charged carriers; and a multiplier region having a multiplication layer; wherein the multiplier region is on a mesa structure separate from the absorber region and is coupled to the absorber region by a bridge for transferring charged carriers between the absorber region and multiplier region.

Abstract: A avalanche mode photodiode array (102) is fabricated using a silicon on insulator wafer and substrate transfer process. The array includes a plurality of photodiodes (100). The photodiodes (100) include an electrically insulative layer (206), a depletion region (204), and first (208) and second (210) doped regions. An interconnection layer (212) includes electrodes (214, 216) which provides electrical connections to the photodiodes. The photodiode array (102) is carried by a handle wafer (217).

Abstract: An imaging device is provided and includes: a photoelectric conversion layer that has a silicon crystal structure and generates signal charges upon incidence of light; a multiplication and accumulation layer that multiplies the signal charges by a phenomenon of avalanche electron multiplication; and a wiring substrate that reads the signal charges from the multiplication and accumulation layer and transmits the read signal charges.

Abstract: An avalanche photodiode according to this invention include a light receiving region 101 surrounded by a ring-shaped trench 13, a first electrode 11 formed on the light receiving region 101, a second electrode 12 formed on the periphery of the ring-shaped trench 13 surrounding the light receiving region, a first semiconductor layer lying just under the first electrode 11, and a second semiconductor layer lying just under the second electrode 12. Conductivity types of the first semiconductor and the second semiconductor are identical.

Abstract: A single-photon avalanche detector is disclosed that is operable at wavelengths greater than 1000 nm and at operating speeds greater than 10 MHz. The single-photon avalanche detector comprises a thin-film resistor and avalanche photodiode that are monolithically integrated such that little or no additional capacitance is associated with the addition of the resistor.

Abstract: A photodetector circuit incorporates an APD detector structure (10) comprising a p? silicon handle wafer (12) on which a SiO2 insulation layer (14) is deposited in known manner. During manufacture a circular opening (16) is formed through the insulation layer (14) by conventional photolithography and etching, and an annular p+ substrate contact ring (18) is implanted in the handle wafer (12) after opening of the window (16). The APD itself is formed by implantation of a p region (20) and an n+ region (22). After the various implantation steps a metallisation layer is applied, and annular metal contacts are formed by the application of suitable photolithography and etching steps, these contacts comprising an annular contact (26) constituting the negative terminal and connected to the p+ substrate contact ring (18), an annular metal contact (28) constituting the positive terminal and connected to the n+ region (22) of the APD, and source and drain contacts (30) and (32) (not shown in FIG.

Abstract: An avalanche photodiode (APD) includes an anode layer, a cathode layer, an absorption layer between the anode layer and the cathode layer, a first multiplying stage between the absorption layer and the cathode layer, a second multiplying stage between the first multiplying stage and the cathode layer, and a carrier relaxation region between the first and second multiplying stages. Each multiplying stage includes, in the direction of drift of electrons, a first layer that is doped with acceptors, a second layer that is substantially undoped, a third layer that is doped with acceptors, a fourth layer that is substantially undoped, and a fifth layer that is doped with donors.

Abstract: The invention relates to a radiation detector (1) for detecting low-intensity radiation, especially for detecting individual photons. The radiation detector includes a plurality of rows of image cells (5) with respective pluralities of image cells (5) disposed one after the other and respective signal outputs (6). The radiation to be detected generates signal charge carriers in the individual image cells (5), the charge carriers being transported along the rows of image cells to the respective signal output (6). A plurality of output amplifiers (7) are connected in parallel to one of the signal outputs each of the individual image cell columns and amplify the signal charge carriers. The invention is characterized in that the output amplifiers (7) include respective avalanche amplifiers (8).

Abstract: Avalanche photodiodes are provided, wherein the APDs provide both high optical coupling efficiency and low dark count rate. The APDs are formed such that their cap layer has an active region of sufficient width to enable high optical coupling efficiency but the APD still exhibits a low dark count rate. These cap layers have a device area with an active region and an edge region, wherein the size of the active region is substantially matched to the mode-field diameter of an optical beam, and wherein the size of the edge region is made small so as to reduce the number of defects included. These APD designs maintain a substantially uniform gain and breakdown voltage, as necessary for practical use.

Abstract: Avalanche photodiodes are provided, wherein the APDs provide both high optical coupling efficiency and low dark count rate. The APDs are formed such that their cap layer has an active region of sufficient width to enable high optical coupling efficiency but the APD still exhibits a low dark count rate. These cap layers have a device area with an active region and an edge region, wherein the size of the active region is substantially matched to the mode-field diameter of an optical beam, and wherein the size of the edge region is made small so as to reduce the number of defects included. These APD designs maintain a substantially uniform gain and breakdown voltage, as necessary for practical use.

Abstract: An avalanche photodiode detector is provided. The avalanche photodiode detector comprises an absorber region having an absorption layer for receiving incident photons and generating charged carriers; and a multiplier region having a multiplication layer; wherein the multiplier region is on a mesa structure separate from the absorber region and is coupled to the absorber region by a bridge for transferring charged carriers between the absorber region and multiplier region.

Abstract: Avalanche photodiodes are provided, wherein the APDs provide both high optical coupling efficiency and low dark count rate. The APDs are formed such that their cap layer has an active region of sufficient width to enable high optical coupling efficiency but the APD still exhibits a low dark count rate. These cap layers have a device area with an active region and an edge region, wherein the size of the active region is substantially matched to the mode-field diameter of an optical beam, and wherein the size of the edge region is made small so as to reduce the number of defects included. These APD designs maintain a substantially uniform gain and breakdown voltage, as necessary for practical use.