Showing papers on "Photodiode published in 1977"

Diffusion lengths in solar cells from short‐circuit current measurements

Abstract: The minority‐carrier diffusion length in the base region of a silicon solar cell has been determined by measuring the short‐circuit current as a function of the wavelength of incident light. The incident light intensity required to produce a given short‐circuit current is a linear function of the reciprical absorption coefficient for each wavelength, and the extrapolation of this linear relation to zero intensity yields the diffusion length. This method is similar to the surface photovoltage and open‐circuit voltage methods; however, the accuracy for high light bias levels appears to be greatly improved.

Method of and apparatus for measurement of blood flow using coherent light

Abstract: An apparatus for measuring the flow parameter of blood flowing in an organ includes a laser and associated optics which effect the illumination of tissues. The laser light, scattered by the tissues, emerges with a spectrum broadened by Doppler effect due to motion of red blood cells in the micro-circulation vessels. The light from the tissues is fed to a photomultiplier tube or photodiode via a pinhole mask and interference filter. The photomultiplier tube or photodiode, as a result of beating of various components of the light it receives, produces as its output signals a homodyne or heterodyne spectrum or both. These output signals are fed, via a low pass filter, to a differentiator, which differentiates the output signals from the multiplier tube or photodiode, which are passed by the filter, with respect to time. The output of the differentiator is fed to a root-mean-square (RMS) detector. The low pass filter passes, for example, signals having a frequency up to about 20 KHz. The output (R) from the detector, which represents the blood flow (average percolation) in the tissues plus shot noise, a constant (S), is fed to a digital voltmeter. The voltmeter produces a visible read-out indicative of the output from the detector. The output from the detector is also fed to a calculating circuit which also receives a signal corresponding to the mean current (I) produced by the photomultiplier or photodiode, the calculating circuit effecting a solution to the equation ##EQU1## Fnorm is a normalized output signal representation of blood flow parameter.

Efficient sprayed In2O3 : Sn n‐type silicon heterojunction solar cell

Abstract: We present results concerning In2O3 (tin‐doped) n‐type silicon heterojunction solar cell. The transparent and conductive In2O3 : Sn layer was made using a very simple, cheap, and quick method. Conversion efficiency up to 10% is reported. Typical parameters under AM1 simulated sunlight are open‐circuit photovoltage Voc=500 mV, short‐circuit photocurrent Isc=32 mA cm−2, and fill factors around 0.6–0.65.

Backside‐illuminated InAs1−xSbx‐InAs narrow‐band photodetectors

Abstract: High‐performance backside‐illuminated photodiodes have been fabricated for the first time from InAs1−xSbx‐InAs heterostructures prepared by liquid‐phase‐epitaxy technique. The peak wavelength can be tuned compositionally from 3.1 to over 7.0 μm at 77 K. The half‐width of the spectral responses as narrow as 1760 A (at 4.0 μm) have been achieved. Internal quantum efficiencies of 90% and zero‐bias‐resistance–area products of 2×107 Ω cm2 have been obtained at 77 K.

InxGa1−xAsyP1−y/InP heterojunction photodiodes

Abstract: The photoelectronic properties of quaternary alloy heterojunction photodiodes made of liquid‐phase‐grown In0.88Ga0.12As0.25P0.75 layers deposited onto p‐doped InP substrates have been investigated experimentally and analytically. It is shown that a typical photodiode with a peak responsivity of 0.26 A/W (at 1.02 μm) has a quantum efficiency of ∼22% at 1.06 μm.

Integrated optical detectors

Abstract: A plurality n of double heterostructure photodiodes are coupled together by (n-1) interleaved n + -p + tunnel junctions to form a multi-layered integrated structure which has an open circuit photovoltage approaching the sum of the open circuit photovoltages of the individual photodiodes. In one embodiment, in which radiation to be detected is made incident normal to the layers, the absorbing layers of the photodiodes get progressively thicker away from the substrate. In a second embodiment, in which the radiation is made incident parallel to the layers, all of the absorbing layers have essentially the same thickness. In a third embodiment, in which radiation is made incident normal to the layers, the structure has a stepped configuration and all of the absorbing layers have essentially the same thickness.

Composition‐tuned PbSxSe1−x Schottky‐barrier infrared detectors

Abstract: Schottky‐barrier photodiodes were prepared by depositing either lead or indium onto p‐type PbSxSe1−x epitaxial films. These photodiodes had 77 °K zero‐bias resistance‐area products of 26–21 000 Ω cm2 as x varied from 0 to 1, respectively. The peak detectivities were close to the background limit and could be composition tuned between 3.7 and 6.9 μm at 77 °K. Narrowband detectors were prepared by using one film as a short‐wavelength cutoff filter and a second film, of slightly different composition, as the detector. These devices exhibit high quantum efficiencies, low half‐bandwidths, and insensitivity to variations in incident angle.

Method of fabricating silicon photodiodes

Abstract: METHOD OF FABRICATING SILICON PHOTODIODES Abstract of the Disclosure Described is a method of fabricating front-illuminated silicon photodiodes having high quantum efficiency, a short response time, (high gain and low excess noise in the case of avalanche diodes), low dark currents and good reliability. In the fabrication of an n+-p-.pi.-p+ APD the method includes the steps of: (1) epitaxially growing a high resistivity .pi.-type silicon layer on a high conduc-tivity p-type silicon substrate; (2) forming an n-type guard ring in the .pi.-layer; (3) forming a p-type channel stop around the guard ring; (4) forming in the .pi.-layer a p-layer by ion implantation and by driving in the implanted ions by heating in a suitable atmosphere; (5) masking the p-layer and introducing phosphorus into the backside to getter defects and/or impurities; (6) ramping the furnace temperature during steps (2) through (5) to reduce crystalline defects; (7) forming a thin n+-layer in the p-layer; (8) forming an anti-reflection and passivation coating on the n+-layer; and (9) forming electrical contacts to the substrate, the guard ring and the channel stop so that the latter two contacts overlap the surface portions of the corresponding metallurgical junctions. The n+-layer is made extremely thin in order to reduce hole injection caused by light incident on that layer, and the ion implantation - drive step (4) and subsequent steps which involve heating are mutually adapted so that the resultant electric field profile in the multiplication region (p-layer) is substantially triangular. A similar process, which omits step (4), is also described for the fabrication of n+-.pi.-p+ photodiodes.

X-ray detecting system having negative feedback for gain stabilization

Abstract: An X-ray detecting system includes a number of X-ray detectors mounted on the periphery of a vertical ring rotatable about a patient to be scanned diametrically opposite from an X-ray tube, slit collimator and chopper wheel mounted on the ring. Each detector includes a scintillator crystal typically of NaI, a photomultiplier tube that receives light from the crystal proportional to the incident X-rays, an amplifier energized by the output of the photomultiplier tube that provides a proportional signal to an LED that energizes both the photomultiplier tube (PMT) to provide light feedback and a photodiode that provides an electrical output signal so that the total current at the PMT anode resulting from X-ray light and LED light is constant. Circuitry is preferably included so that the LED supplies only the chopped part of the X-ray equivalent light signal with practically no d-c component.

Photo electric light detection devices

Abstract: A photo electric light detection device comprising an array of photodiodes is disposed at an end face of a light conducting rod in order to produce an output signal proportional to light incident on the surface of the rod and transmitted to the end face by total internal reflection. The array of photodiodes is subdivided into high and low pass frequency sub-arrays and the output signals from the sub-arrays are summed and processed to compensate for stray light. The device is useful in connection with a line scanner for detecting anomalies in a moving band.

Servo control apparatus

Abstract: A monolithic photosensor array comprises first, second and third identical photodiodes. A light emitting diode illuminates the third photodiode continuously. An occluder disc is rotatably driven from the shaft of a servo motor between the light emitting diode and the first and second photodiodes. The disc is formed with a plurality of circumferentially spaced apertures which alternately cover and uncover the photodiodes which produce quasisinosoidal position signals in response thereto, the position signals of the first and second photodiodes being relatively 90° out of phase. A computing circuit produces a motor shaft velocity command signal corresponding to the number of steps the shaft must rotate from the initial position to the new desired position and progressively reduces the magnitude of the velocity signal in response to the position signals. A differentiating circuit differentiates the position signals and their inversions and a commutator produces an actual velocity signal by sampling the peak values of the differentiated position signals. A comparator compares the velocity signal with the velocity command signal and produces an error signal corresponding to the difference therebetween which is fed to the motor as a drive signal. A sensor senses the output voltage of the third photodiode and an intensity control circuit adjusts the current flow through the light emitting diode until said output voltage has a predetermined value, thereby compensating for ambient temperature and other variations of all three photodiodes. A stable reference voltage for the apparatus is derived from the sensor.

The response of small photovoltaic detectors to uniform radiation

Abstract: The short-circuit photocurrent of a small photodiode under uniform illumination is discussed for the case of diffusion length larger than the absorption depth. Lateral response, resulting from carrier diffusion in the substrate near the photodiode, is taken into account. Numerical results of a two-dimensional analysis are presented and compared to one-dimensional approximations. Effects of various parameters, such as surface recombination velocity and excess carrier lifetime on the lateral response are discussed.

Electro-optical branching device and method of manufacturing the same

Abstract: The invention relates to optical communications by bundles of optical fibres. More particularly, the invention relates to a branching fiber optic connector device for optically and mechanically connecting two bundles of optical fibres with a single optical fibre and for supplying an electrical signal characteristic of the incident optical energy obtained by extracting part of the radiation in said fibre by means of a photodiode sealed to said fibre after removal of the cladding over a surface corresponding to the detecting surface of the photodiode, the refractive index of the sealing material being higher than the refractive index of the cladding.

Avalanche photodiode with reduced avalanche breakdown voltage

Abstract: An avalanche photodiode has a rectification barrier formed by an n+ -layer and a p-type layer of a low doping concentration. A thin p-layer having a higher doping concentration than a p- -layer is inserted between the p- -layer and a π-layer, whereby the avalanche breakdown voltage of the photodiode is lowered considerably.

Interlaced photodiode array employing analog shift registers

Abstract: A photodiode array employing an analog shift register with a line of interlaced photodiodes. Alternate diodes are coupled to one of a pair of analog shift registers which are disposed on opposite sides of the line of photodiodes. An "anti-blooming" polysilicon line and a "transfer" polysilicon line are disposed along each side of the line of photodiodes adjacent to the shift registers. Each of the diffused region forming the photodiodes are coupled by a metal line to another diffused region formed between the anti-blooming and transfer polysilicon lines. This latter region acts as a remote, common region for both the anti-blooming function and transfer function.

Method for regulating the output power of a semiconductor laser

Abstract: Arrangement for regulating the output power of a semiconductor laser for a data transmission system including a light conductive fiber through which the laser power is transmitted and a photodiode which is responsive to light energy produced by the laser and whose output signal is utilized, possibly after appropriate amplification, to regulate the laser current. The photodiode is a thin-film photodiode which is transparent for the light frequencies to be transmitted via the light conductive fiber and is inserted in the light-conductive fiber used to transmit the signals.

A fast sample and hold charge-sensing circuit for photodiode arrays

Abstract: An on-chip charge-sensing circuit with a feedback loop has been designed for improving the charge-transfer speed in photodiode arrays. Its large output voltage swing combined with improved speed performances, makes this circuit well-suited for OCR applications, especially low-cost data capture devices. Sample and hold operation can easily be performed without increasing the Si real estate, making parallel output feasible with frame rates of 3 kHz for arrays with 500 pixels. Experimental arrays were built in standard p-channel aluminum-gate technology.

AC silicon PN junction photodiode light-valve substrate

Abstract: There is disclosed a single crystal silicon charge storage apparatus suitable for use in an alternating current driven liquid crystal light valve having therein a PIN photodiode structure. The charge storage medium is made of a high resistivity substrate on which an MOS capacitor is formed having fast photoelectric transient response an capable of operating over a wide frequency range. A PIN photodiode structure is provided on one side of the substrate next to the MOS capacitor to deplete the substrate of its mobile charge carriers during a portion of the AC cycle and to collect the electric field-guided signal representing charge carriers that are generated or introduced into the substrate by an input mechanism. The signal from the substrate is electrically coupled through high-reflectivity mirrors and light blocking layers to the liquid crystal.

An integrated optical waveguide and charge-coupled-device image array

Abstract: The device structure and experimental operation of an integrated optical waveguide and charge-coupled device (CCD) detector array are considered. The use of silicon as a substrate allows direct fabrication of the CCD detector array and a thermally oxidized layer of SiO 2 forms an effective substrate for waveguide deposition. The detector array is composed of a two-phase overlapping-gate CCD with first-level polycrystalline silicon electrodes and second-level aluminum electrodes connected in parallel by means of a series of gates to an array of pbotodiodes. In the photodiode region the SiO 2 layer is tapered to a termination so that with minimal scatter, light is multiply refracted into the detector region. The center-to-center detector element spacing of the device fabricated and successfully operated is 32 μm. Optimum detector length is considered as a function of waveguide thickness. The integrated waveguide-CCD array is expected to become an integral part of various signal-processing devices.

Method of making a gap UV photodiode by multiple ion-implantations

Abstract: An ultraviolet sensitive photodiode is formed in a body of first conductivity type GaP. A region of second conductivity type with a graded impurity distribution is formed in the body, and a thin layer (preferably about 100A to 300A) is then removed from the front surface of the body. The removal of the thin layer significantly enhances the performance of the UV sensitive photodiode.

Performance of p-i-n photodiode compared with avalance photodiode in the longer-wavelength region of 1 to 2 μm

Abstract: The signal/noise ratio is estimated in comparing p–i–n and a.p.d. photodetectors. In the longer-wavelength region, the p–i–n diode is expected to be superior to the a.p.d., although, in the shorter-wavelength region, under 1.0μm, the converse is true.

Photo electric biased photo diode operational amplifier

Abstract: A circuit useful in replicating the current produced in a photo diode operated as a current source at zero bias. A second scaled area photo diode is used to bias the circuit to maintain the zero bias over a wide range of illumination levels. The circuit operates in the picoampere range and is linear over at least six orders of magnitude.

Integrated optical detector array, waveguide, and modulator based on silicon technology

Abstract: An integrated optical (IO) hybrid circuit consisting of a photodetector array, waveguide, and acousto-optic modulator on a common silicon substrate has been fabricated. This IO hybrid circuit is a major step in the development of a combination optical-electronic processing system. In this device an array of p-n junction photodiodes was fabricated on a 2-in silicon wafer and a 7059 glass waveguide film sputtered over an SiO/SUB 2/ insulating layer on the wafer. Another SiO/SUB 2/ layer was deposited under the transducer electrode. The transducer was a 40-MHz lithium niobate rotated Y-cut crystal. A prism was used to couple in the light beam from a 5 mW He-Ne laser. The guided light beam was directed at one of the diodes in the array and pulsed RF signals were applied to the transducer. Oscillator frequencies of 40 MHz and 120 MHz were separately applied. Modulation depths of greater than 25 percent were produced. The fabrication of the optical guide photodiode and electrical interconnections on a single silicon wafer utilized standard IC fabrication techniques.

Wideband optical isolator

Abstract: A linear voltage controlled current sink is used to power a linear LED with fast optical rise time. The signal is transmitted through a small aperture in a grounded shield plate. The receiver is a PIN photodiode with fast optical rise time.

Optimizing Photodetectors for Radiation Environments

Abstract: In an ionizing environment, the photodetector in an optoelectronic data link is a major source of unwanted signal An analysis is presented of the analog signal response of Si and other photodiode materials to light and to ionizing radiation for single-pass, two-pass, and multipass optical detectors Since the analog signal analysis represents a worse case calculation, photodiodes in digital data links will exhibit even higher radiation tolerances Maximum allowable radiation dose rates are determined as a function of the effective collection depth which is defined as the width of the collection region for minority carriers These calculations demonstrate that the proper selection of the detector material will allow signal detection in the presence of dose rates as high as 2 × 106 rads/sec per mW/cm2 of light power in a realistic photodiode structure The parameters used in the calculations for Si are verified by experiment