Showing papers on "Photodiode published in 1992"

Effect of dead space on gain and noise of double-carrier-multiplication avalanche photodiodes

Abstract: The effect of dead space on the statistics of the gain in a double-carrier-multiplication avalanche photodiode (APD) is determined using a recurrence method. The dead space is the minimum distance that a newly generated carrier must travel in order to acquire sufficient energy to become capable of causing an impact ionization. Recurrence equations are derived for the first moment, the second moment, and the probability distribution function of two random variables that are related, in a deterministic way, to the random gain of the APD. These equations are solved numerically to produce the mean gain and the excess noise factor. The presence of dead space reduces both the mean gain and the excess noise factor of the device. This may have a beneficial effect on the performance of the detector when used in optical receivers with photon noise and circuit noise. >

Video camera, imaging method using video camera, method of operating video camera, image processing apparatus and method, and solid-state electronic imaging device

Abstract: A suitable image is obtained of a subject in which the difference in luminance between a bright area and a dark area is very large. The dark area is properly exposed and first image data is obtained. The bright area is properly exposed, and second image data is obtained. The first image data pertaining to the bright area is replaced with the second image data, thereby obtaining composite image data. This is accomplished using an array of photodiodes comprising two sets of photodiodes, one set of the photodiodes comprising filters, and the respective sets of photodiodes output signals to respectively different transfer paths for signal processing.

Silicon-based semiconductor heterostructures: column IV bandgap engineering

Abstract: The use of strained layer epitaxy to grow high-quality Ge/sub x/Si/sub 1-x//Si heterostructures and their application to a wide range of heterostructure devices are addressed. The author reviews the mechanisms of strained layer growth, the bandstructure of the resulting material, and its use in test devices, including superlattice avalanche photodiodes for fiber optic communication, intrasubband optical detectors and arrays operating in the 10-15 mu m wavelength range, mobility enhanced modulation-doped transistors, heterojunction bipolar transistors with cutoff frequencies of 75 GHz, and negative resistance devices based on resonant tunneling and real-space carrier transfer. >

Multiple- and single-shot autocorrelator based on two-photon conductivity in semiconductors

Abstract: Two-photon-induced conductivity has been observed in Si and GaAsP photodiodes and in a CdS photoconductive cell at room temperature and applied to the ultrashort optical pulse measurement with a simplified Michelson-type arrangement. The efficiency of the two-photon conductivity is found to be 3 × 10−14I A/W, where I is the intensity of the incident pulse in watts per squared centimeter. A single-shot pulse-width measurement has also been performed by using a two-dimensional silicon CCD array. Use of these inexpensive photodetectors with nonlinear characteristics has proved to be convenient for intensity correlators because of their instantaneous response to temporal coincidence of optical pulses and ease of optical arrangement.

Effect of dead space on gain and noise in Si and GaAs avalanche photodiodes

Abstract: The effect of dead space on the mean gain, the excess noise factor, and the avalanche breakdown voltage for Si and GaAs avalanche photodiodes (APDs) with nonuniform carrier ionization coefficients are examined. The dead space, which is a function of the electric field and position within the multiplication region of the APD, is the minimum distance that a newly generated carrier must travel in order to acquire sufficient energy to become capable of causing impact ionization. Recurrence relations in the form of coupled linear integral equations are derived to characterize the underlying avalanche multiplication process. Numerical solutions to the integral equations are obtained and the mean gain and the excess noise factor are computed. >

Integrated lead frame pulse oximetry sensor

Abstract: Disclosed is an integrated lead frame pulse oximetry sensor which includes a thin metal lead frame (12) to which is connected light emitting diodes (16, 18) and a photodiode chip (20) for the purpose of emitting light and detecting light respectively. The thin metal frame (12) is deformable to attach to perfused tissue. The lead frame (12) has a very low mass which diminishes its susceptibility to motion induced artifact.

Semiconductor laser device

Abstract: PURPOSE:To accurately feed back to a laser driving circuit by forming a photodiode film for monitoring directly or through a film for regulating a reflectivity on a back beam emitting end face. CONSTITUTION:In a semiconductor laser, electrodes 2, 2 are formed on the upper and lower surfaces of a laser diode chip 1 formed of an n-type region 1a, a p-type region 1b and a waveguide 1c, a thin film 3 for reducing the reflectivity is formed on the front end of the chip 1, a thin film 4 is formed on the rear end face, a photodiode film 5 is formed on the film 4, and a metal film 6 is further formed on the film 5. When a current flows to the chip 1, electrons are fed from the region 1a to the waveguide 1c, holes are fed from the region 1b to the waveguide 1c to generate a light, the generated laser light is propagated through the waveguide 1c to be irradiated from the front end of the chip 1 as a front beam 7, the other part is absorbed to the film 5 to generate a monitoring current. A laser driving circuit is controlled based on the monitoring current to control the front beam.

A planar InP/InGaAs avalanche photodiode with floating guard ring and double diffused junction

Abstract: The authors discuss the fabrication, performance, and design of a novel, planar In/sub 0.53/Ga/sub 0.47/ As/InP separate absorption and multiplication region avalanche photodiode (SAM-APD) with floating guard rings and a double Zn diffused junction. The APD, grown by both vapor phase epitaxy and metalorganic vapor phase epitaxy, is observed to have a uniform gain of 85, a minimum primary dark current density of 5*10/sup -6/ A/cm/sup 2/ at 90% of breakdown, and a capacitance of 0.4 pF for a front-side illuminated device. Both experimental and analytical results show that the double-diffused floating guard ring structure prevents edge breakdown, and also greatly reduces the electric field along the semiconductor/insulator surface. The operation mechanisms and the optimum design of the planar APD based on a two-dimensional device model are discussed. >

A combined Thomson–Rayleigh scattering diagnostic using an intensified photodiode array

Abstract: A combined Thomson–Rayleigh scattering device is discussed. It consists of a Nd:YAG laser as a light source in combination with a multichannel detection technique consisting of a gated light amplifier in combination with an optical multichannel analyzer. Special attention is focused on the analysis of the measured spectra. Including convolution methods and taking into account weak coherent effects increases the dynamic range and the accuracy of the measured electron density ne and temperature Te and neutral particle density n0. Accuracies of 1%–4% for ne, 2%–6% for Te, and 10%–50% for n0 depending on the plasma condition are obtained. The dynamic range for ne is 7×1017–1021 m−3, for n0 is 1020–1023 m−3 and for Te is 1000–50 000 K.

Intra-oral sensor for computer aided radiography

Abstract: An intra-oral sensor for computer aided oral examination by means of low dosage x-rays in place of film and developer. The intra-oral sensor is exceedingly thin for proper mouth placement and in situ maneuvering, with an active area substantially equivalent to corresponding dental film sizes and a thickness of no more than about 3 mm. In addition, the sensor contains limited electronics and no optical elements, and is resistant to moisture and heat and is readily autoclaved. The sensor, consists of a thin, large area semiconductor image array such as a modified charge coupled device (CCD) or photodiode array, coated with a thin, epitaxial growth of a material such as thallium doped cesium iodide CsI(Tl). The coated sensor is bonded to and supported on a passivated ceramic chip, and has an integrated signal amplifier, with the entire assembly being coated with a protective inert plastic layer, e.g., polytetrafluoroethylene, which is pervious to x-ray radiation. The CsI(Tl) is sensitive to x-ray photons, efficiently converting them into visible photons in the 500-600 um range. To reduce light spreading within the CsI(Tl) layer, growth of the CsI(Tl) layer is directed into narrow (20 um) columns. Visible photons are detected by the large area semiconductor array and the output is monitored by a computer until polling of the CCD or photodiode array indicates that there is no further conducting. A signal thereafter causes a read out of the electrical charges for translation from analog to digital signals of images with computer display and analysis.

Grating spectrograph integrated with photodiode array in InGaAsP/InGaAs/InP

Abstract: A grating spectrograph integrated monolithically for the first time in the InGaAsP system with a photodiode array for a dense WDM application is presented for the 1.5 mu m wavelength region. The chip provides 42 wavelength channels with a spacing of 4 mm, a channel crosstalk of approximately -15 dB, an internal photodiode efficiency of 90%, and a photodiode capacitance of 0.33 pF. The chip needs no optical adjustments. It is therefore well suited for mass production. >

First results on the hybrid photodiode tube

Abstract: The performance of a new breed of light detectors based on a photocathode followed by a planar silicon diode working in the bombarding mode is reported This detector was developed by the LAA project in order to produce a fast light detector capable of covering a span of the more than 4 orders of magnitude of linearity required by the scintillating fibre and lead (“spaghetti”) calorimeter Linear signals from single, to more than 10 6 photoelectrons per pulse were measured The general characteristics of this detector are reported here

Performance analysis of direct-detection optical CDMA communication systems with avalanche photodiodes

Abstract: Direct-detection optical code-division multiple-access (CDMA) communication systems with avalanche photodiode (APD) photodetectors are investigated. A Chernoff upper bound, modified Chernoff upper bound, and Gaussian approximation on the probability of bit error are presented for general APDs and arbitrary

Scanning multichannel technique for improved spectrochemical measurements with a CCD camera and its application to Raman Spectroscopy

Abstract: In continuation of work performed with the application of the scanning multichannel technique in combination with a photodiode array and a single monochromator we show in the present paper a similar technique combining a CCD camera with a double monochromator system with additive dispersion. Special emphasis is given to a discussion of the reproduction of spectral features with small bandwidth. Examples of applications of this technique are given in terms of high-resolution Raman spectroscopy of gases. This technique is not restricted to this type of optical spectroscopy, but can be universally applied to all spectroscopic methods where CCD detection is used.

Solid-state image pickup device

Abstract: PURPOSE:To obtain an almost constant high sensitivity in an entire exposing area by connecting an MOS transistor to set an initial state with the base of a phototransistor; and connecting the gate electrode of the MOS transistor with the emitter of the phototransistor. CONSTITUTION:An MOS transistor 13 which applies a reference voltage is connected with the base of a phototransistor 11 being a light receiving element, and the gate electrode of the MOS transistor 13 is connected with the emitter of the phototransistor 11. Therefore, the potential of the the emitter of the phototransistor is turned back to the initial state, and simultaneously the potential of base is turned back to the initial state in which the phototransistor operates a sufficient amplitude operation. Then, the storage of an optical charge is operated in the base area, so that the potential difference between the base and the emitter can keep a sufficient size for the amplitude operation even under a low exposure condition. Thus, a photoelectric conversion characteristic which indicates the constant high sensitivity can be obtained in the entire exposing area in which an image sensor is used.

Color sensor employing optical fiber bundles with varied diameters

Abstract: A device (1) for photoelectrically sensing the color of an object (18) includes a plurality of light emitting diodes (4, 6, 8) emitting light in a narrow range of wavelengths and where the light is transmitted through a corresponding fiber optic bundle (10, 12, 14) with a diameter in proportion to the transmission loss of the bundle and in inverse proportion to the emitted light energy of the corresponding light emitting diode and in proportion to the spectral response of a receiving photodiode (24). A receiving section (22) utilizes a PIN type photodiode (24) with an input section (40) that matches the shape of a receiving optical fiber bundle termination (42) where the photodiode (24) converts the reflected light from the object (18) into electrical signals which are then processed by a microprocessor (28) which also controls the activation of the light emitting diodes (4, 6, 8) and outputs a signal indicative of the color of the object (18).

Chirping characteristic and frequency response of MQW optical intensity modulator

Abstract: The spectral linewidth enhancement factor and frequency responses of electro-absorption-type optical-intensity modulators, especially InGaAs/InAlAs MQW modulators, are described. A method of exactly estimating the value of the alpha factor is presented under the nonlinearity of extinction-ratio characteristics. For measuring the frequency response of modulators, the sideband strength of the modulated output light with an optical spectrum analyzer, is analytically compared with the microwave power of photodiode direct detection with an electrical spectrum analyzer. >

A model for the trap-assisted tunneling mechanism in diffused n-p and implanted n/sup +/-p HgCdTe photodiodes

Abstract: A theoretical model for the trap-assisted tunneling process in diffused n-on-p and implanted n/sup +/-on-p HgCdTe photodiodes is presented. The model describes the connection between the leakage current associated with the traps and the trap characteristics: concentration, energy level, and capture cross sections. It was observed that the above two types of diodes differ in the voltage dependence of the trap-assisted tunneling current and dynamic resistance. The model takes this difference into account and offers an explanation of the phenomenon. The good fit between measured and calculated DC characteristics of the photodiodes (for medium and high reverse bias and for temperatures from 65 to 140 K) supports the validity of the model. >

Tunneling and 1/f noise currents in HgCdTe photodiodes

Abstract: The 1/f noise currents and the dc dark current–voltage characteristics are measured over a wide range of reverse bias voltages (0≤Vd≤−1.5 V) and operating temperatures (30–120 K). The diodes are fabricated by ion implanting boron (n+) on bulk p‐type material with x≊0.22. Native anodic sulfide in combination with deposited ZnS is used for surface passivation. The dc dark currents of the photodiodes are modeled to extract the tunneling currents from the measured dark currents. The modeling takes into consideration diffusion, generation–recombination, and the two types of tunneling currents (trap assisted tunneling and band to band tunneling). The measurements demonstrate that the dominant mechanism that produces 1/f noise in HgCdTe photodiodes is tunneling, in particular trap assisted tunneling. The correlation between the 1/f noise currents and the dc tunneling currents is given by In=α(It)β(f )−1/2, where It is the tunneling current. The empirical factors β and α are approximately β≊0.5 and α≊1×10−6 for a...

Submillimeter-wave detection with superconducting tunnel diodes

Abstract: The review presents a theoretical framework for understanding submillimeter detection using an optical photodiode theory. Both gain and noise in the superconductor-insulator-superconductor (SIS) mixer are described in terms of mixing on a photodiode. The role of impedance matching in the proper design of an SIS mixer is described. A variety of methods for achieving good impedance match at submillimeter frequencies are presented. The state of the submillimeter SIS mixer art as practiced in a variety of laboratories is described and summarized. >

Development of a medical fiber-optic pH sensor based on optical absorption

Abstract: A new fiber-optic pH sensor system has been developed. The sensor uses an absorptive indicator compound with a long wavelength absorption peak near 625 nm; change in absorption over the pH range 6.8 to 7.8 is reasonably linear. The sensor is interrogated by a pulsed, red LED. The return light signal is split into short- and long-wavelength components with a dichroic mirror; the respective signals are detected by photodiodes, and their photocurrents are used to form a radiometric output signal. In laboratory tests, the sensor system provided resolution of 0.01 pH, accuracy of +or-0.01 pH, and response time of 30-40 s. Following gamma sterilization, laboratory sensor testing with heparinized human blood yielded excellent agreement with a clinical blood gas analyzer. Excellent sensor performance and low cost, solid-state instrumentation are hallmarks of this sensor-system design. >

Self‐calibration of semiconductor photodiodes in the soft x‐ray region

Abstract: A self‐calibration procedure is presented for semiconductor photodiodes to be used as detectors in the soft x‐ray region. In this procedure the spectral responsivity is calculated according to a model from experimentally accessible parameters of the detector. The thicknesses of the dead layer and the space charge region as well as the diffusion length have been determined in monochromatic radiation by investigating the angular dependence of the photocurrent. The mean energy for electron‐hole pair creation has been determined in calculable undispersed synchrotron radiation of the primary standard source BESSY. The obtained uncertainties of the spectral responsivity in the photon energy region between 150 and 2500 eV are ≤4.2% for newly developed Si n on p diodes and ≤6% for GaAsP/Au diodes. The calibrated photodiodes were used to determine the quantum efficiency of photoemissive gold diodes which is up to four orders of magnitude lower than that of semiconductor photodiodes.

60 GHz sources using optically driven heterojunction bipolar transistors

Abstract: Millimeter wave sources at 60 GHz have been demonstrated using optically driven heterojunction bipolar transistors configured as photodetectors. Two techniques were used to optically generate the millimeter waves; the mixing of two cw lasers and the mode locking of a semiconductor laser. The millimeter wave power generated from these two configurations was radiated into free space using integrated planar twin‐dipole antennas and heterodyne detected with signal‐to‐noise ratios ≳40 dB. As part of these experiments, the dc optical gains and quantum efficiencies of the heterojunction bipolar transistor photodetectors were determined.

Integrated grating/detector array fabricated in silicon using micromachining techniques

Abstract: Silicon bulk micromachining techniques have been employed to fabricate an integrated grating and detector array in silicon for operation in the visible and near-infrared spectral range. Two wafers are machined in such a way that an optical path of about 4 mm in length is obtained in which dispersed light from a 32-slit diffraction grating is projected onto an array of photodiodes. The wafers are subjected to an electrochemically controlled etch. The interior of one of the wafers is subsequently coated with a reflective film. The grating and the array of photodetectors are integrated in the second wafer, which remains uncoated. The wafers can be bonded using the direct silicon-to-silicon fusion bonding technique. The functional division into a reflective wafer and a grating/readout wafer greatly simplifies the integration of the complete device in a smart silicon sensor.

Dark current analysis and characterization of In/sub x/Ga/sub 1-x/As/InAs/sub y/P/sub 1-y/ graded photodiodes with x>0.53 for response to longer wavelengths (>1.7 mu m)

Abstract: The dark current properties of In/sub x/Ga/sub 1-x/As photodiodes, where x is varied from 0.53 to 0.82 for extending the long wavelength cutoff from 1.7 to 2.6 mu m, are described. Detailed analyses of optoelectrical parameters of In/sub 0.82/Ga/sub 0.1/As photodiodes are presented. Dark current, which is a critical parameter and limits the operation of the photodiode, is analyzed and compared with the experimental values. Typical characteristics of photodiodes with cutoff wavelengths of 1.7 mu m (x=0.53), 2.2 mu m (x=0.72), and 2.6 mu m (x=0.82) are presented. The typical and best values of the dark currents obtained are presented. >

High time resolution x-ray measurements with an avalanche photodiode detector

Abstract: An avalanche photodiode (APD) detector has been developed for x‐ray timing measurements with a subnanosecond time resolution. The performance of the APD detector was investigated with synchrotron x‐ray beams in multi‐ and single‐bunch runs at the Photon Factory (PF) ring. A time resolution of 0.28 ns (FWHM) and a peak‐to‐background ratio of more than 107 were obtained from the main peak of 14.4‐keV x rays in a single‐bunch time spectrum. The intrinsic efficiency and the counting‐rate capability were also measured. As an application with a high time resolution, time spectra of quantum beats in nuclear resonance of 57Fe were observed with the APD detector at the undulator beam line BL‐NE3 of the TRISTAN accumulation ring; the first peak of the beats was completely separated from the prompt peak of the non‐nuclear components with a good time resolution and the beat structure was sharply seen to the range of ≳100 ns later with a very low background.

Industrial CMOS technology for the integration of optical metrology systems (photo-ASICs)

Abstract: With ‘photo-ASICs’ comprising light-sensitive structures, light-emitting devices and analog and digital circuits, complete optical metrology systems can be integrated on a single chip. We report the realization of key components of such photo-ASICs using an industrual IC CMOS process. We achieve photodiodes with an external quantum efficiency of 50–80% in the visible spectrum and position-sensitive devices (PSDs) with a spatial non-linearity of around 0.3%. We demonstrate surface-channel CCDs with a charge-transfer efficiency of 99.8% at room temperature, as well as bucket-brigade devices (BBDs) with a lower charge-transfer efficiency of 96%. Light-emitting diodes (LEDs) are realized, emitting infrared light at 1160 nm (forward biased) and broadband visible yellow light with a spectral maximum at 640 nm (reverse biased). We discuss simple applications of passive photo-ASICs, such as a centroid detector, a 3-D camera, a motion detector and a focus sensor, used to obtain a relative measure for the local focus of an optically imaged scene, for example, in a photographic camera.

InGaAsP/InAlAs superlattice avalanche photodiode

Abstract: The fabrication of an InGaAsP-InAlAs superlattice avalanche photodiode using a gas source molecular beam epitaxy is discussed. A quaternal alloy of InGaAsP was used for the well layers in order to suppress the dark current due to the tunneling effect. With this structure, the valance band discontinuity almost vanishes and a gain bandwidth of 110 GHz was obtained. >

Self-monitoring semiconductor laser device

Abstract: The present invention is a semiconductor laser having an integral photodiode and/or modulator. The integrated structure comprises a quantum well active region sandwiched between a pair of distributed Bragg reflector stacks for emitting laser light transverse to the planes of growth. An intrinsic layer and a doped semiconductor layer are disposed on one of the reflector stacks for forming, in combination with the outer layer of the stack, a photodiode in the path of emitted light. The diode can be used either to monitor the laser power or to modulate the laser output. The device is particularly suited for fabrication and testing in large arrays and, in addition, has the advantages of a circular, low divergence optical output, inherently single mode operation, and a high two-dimensional packing density.