Showing papers on "Photodiode published in 1971"

Electrical Properties of Semiconductor Photodiodes with Semitransparent Films

Abstract: High speed photodiodes with semitransparent film-semiconductor junctions, which behave as Schottky barriers, are designed and prepared. The optimized width of the depletion layer of the photodiode is calculated for the selected cut-off frequency. The relations between transmittance and sheet resistivity are studied with some films of semiconducting compounds, which affect the gain and response time of photodiodes. The photodiodes, fabricated by the deposition of the semitransparent films of CdS or CU2Se on Si, have high frequency response and the cut-off frequency of Cu2Se-n.Si photodiodes is higher than 4 GHz.

TYPE CONVERSION AND n‐p JUNCTION FORMATION IN Hg1−xCdxTe PRODUCED BY PROTON BOMBARDMENT

Abstract: We have fabricated n‐p junction photovoltaic detectors in Hg1−xCdxTe with x=050, 031, and 025 using proton bombardment to create the n‐type layer Peak detection sensitivities were in the wavelength range 16–6 μm Although high‐sensitivity photodiodes were obtained with each composition, the best results were obtained with the x=031 material, which has a peak response at 38 μm At 77°K, 15‐mil×15‐mil diodes made with this material had zero‐bias impedances of several megaohms The peak detectivity at 38μ was 9×1011 cmHz1/2/W in reduced background and the quantum efficiency at the peak was 29%

Schottky barrier phototransistor

Abstract: Disclosed is a metal-semiconductor-metal phototransistor formed by a pair of closely spaced, thin metal films in rectifying contact with the surface of a lightly doped p-type indium arsenide substrate. The spacing between the metal films is substantially less than the diffusion length of a minority carrier in the indium arsenide at the operating temperature, which is on the order of -78 DEG C. One metal film may be considered the collector region, the semiconductor material the base region, and the other metal film the emitter region. When the transistor is biased like an NPN transistor, the collector current is varied in proportion to the radiation striking the base region generally in the same manner as a photodiode, but the current modulation is many times that produced by a photodiode for a given radiation level.

Highly reliable strip width gauge

Abstract: The strip width gauge described herein is capable of measuring strips to an accuracy of 50 microinches. In particular, it is applied herein to measuring the width of magnetic tape. The measurements are accomplished by aligning, at each edge of the strip, a light emitting diode on one side of the strip and a photodiode on the other side of the strip. The amount of light reaching the photodiode from its associated light emitting diode will depend upon how much light is intercepted by the strip. The output from the two photodiodes is summed. By summing the outputs, the total is independent of lateral movement of the strip. Light emitting diodes are used so that they might be excited by a signal whose frequency is well above normal power line frequency. The higher frequency signal picked up at the photodiodes can then be either analyzed on an AC basis or rectified and analyzed on a DC basis. Additional photodiodes may be provided as reference photodiodes. The reference photodiodes monitor changes in light emission from the light emitting diodes. Their outputs are also summed, and a difference amplifier takes the difference between the edge-sensing photodiodes and the reference photodiodes.

Video signals and switching transients in capacitor-photodiode and capacitor-phototransistor image sensors

Abstract: A new configuration of the capacitor-photodiode type of image sensor is described which results in appreciable reduction of switching transients at the sensor's output. The modification consists of replacing the photodiode by a phototransistor operating in the common base configuration. A 32 × 32 element array capable of operating in either the photodiode or phototransistor mode was fabricated. The dynamic range, transfer characteristic, and switching transient voltage were calculated for both modes and compared with experiment. For the experimental array an order-of-magnitude improvement in signal-to-noise ratio has been realized in the transistor mode of operation.

Photodiode apparatus for reducing beam drift of a cathode ray tube display system

Abstract: Apparatus for detecting and correcting drift and position errors of an electron beam due to electrical transients or mechanical vibration in a cathode ray tube display system including a diode array located in the path of the scanning electron beam. When the beam is properly directed, a predetermined output signal matrix from the diode array indicates that the beam is on target; if the beam drifts, a different output signal matrix indicates such drift and a servomechanism coupled to the diode array and to the beam deflection circuitry corrects the deflection of the beam in response to signals from the diode array.

Laser energy monitor circuit

Abstract: A laser energy monitor circuit. A fixed fraction of the energy output of a laser is diffused and then directed to a photodiode, and the diode output current is integrated. The integrated signal is transferred to a peak detector which, in turn, drives an FET transistor. The output of the transistor, which may persist for many minutes even in the case of a nanosecond laser pulse, drives a meter and thus provides an extended visual indication of the energy in the pulse.

Bottle inspection apparatus

Abstract: An integrated photocell device for bottle inspection comprises a multiplicity of inspection photodiodes and a level sensing photodiode, which measures the average light transmission through a bottle, arranged in a suitable array for scanning an area of a bottle to be inspected. The level sensing diode is in the form of a grid distributed over the photocell device and the inspection diodes are disposed within the grid. The inspection diodes are each connected in an electrical circuit which is adapted to be triggered by a pulse applied thereto and to restore to its initial state within a time determined by the intensity of the illumination of the photodiode. The individual inspection circuits are connected in parallel to a load resistor, the output voltage across which drops to zero when all the circuits have restored to their initial states. The level sensing diode is connected in a similar circuit to each inspection diode and is connected to a separate load resistor. Means is provided for comparing the times taken for the two output voltages to return to zero, after the application of a pulse, in order to determine whether or not a bottle being scanned by the device should be rejected as being dirty or faulty.

Photometer including variable amplification and dark current compensation

Abstract: Apparatus for measuring the illumination from a source of light is disclosed in accordance with the teachings of the present invention wherein a photodiode exhibiting a substantially uniform spectral sensitivity within a defined range generates a current proportional to the intensity of illumination thereon. Operational amplifier means including a first operational amplifier having a constant closed loop amplification factor connected in series relationship with a second operational amplifier exhibiting a selectively variable closed loop amplification factor amplifies the current generated by said photodiode to provide a voltage that is proportional to the intensity of the illumination of said photodiode. Indicating means may be coupled to said operational amplifier means to provide an indication of the intensity of said illumination.

Exposure meter employing photodiode

Abstract: Exposure meter using a photodiode, wherein open-circuit voltage of the photodiode is applied to the gate of a field-effect transistor. Between the source of said field-effect transistor and the negative terminal of a power source, a variable resistor is inserted and is interlocked with at least one of the exposure factors of the film sensitivity, the aperture of a photo-lens and the exposure time, so as to vary the value of the resistance of the variable resistor.

Optimum high gain-bandwidth phototransistor structure

Abstract: The fabrication of two semiconductor structures such as a high speed, optimum sensitivity photodiode and a maximum gainbandwidth transistor on the same wafer is described. A thin, low resistivity layer is formed on a higher resistivity substrate and the diode junction is then formed in one part of the wafer by diffusing the junction-forming region through the layer and down into the substrate. This provides a diode of low capacitance and optimum light sensitivity. The transistor is then formed in another part of the same wafer by first diffusing the basecollector junction into the thin layer followed by a diffusion therein of the emitter-base junction. This diffusion into the layer is very shallow and results in a high gain-bandwidth transistor. The photodiode structure is affected very little by the processing required to form the transistor, thus allowing each structure to be independently optimized.

Silicon p-n junction photodiode characteristics with variable drift field in the diffused region

Abstract: The continuity equation for the minority carriers, considering the actual field variation in the diffused region of a photodiode with a complementary-error-function impurity distribution, has been solved in terms of a power series. The essential parameters, such as excess minority-carrier profile, short-circuit current, surface loss and collection efficiency have been calculated.

InAs charge-storage photodiode infrared vidicon targets

Abstract: InAs charge-storage photodiode arrays for electron-beam vidicon applications are being developed. The InAs array diodes exhibit sufficiently low reverse leakage currents for the diode to be operated in a charge-storage mode with an electron beam scannig at the conventional TV scanning rate of 1/30 s, at a diode temperature of 77 ° K. The meaured typical reverse leakage current density near liquid-nitrogen temeperature is in the range of 5 × 10^{-10} A/cm^{2} at the reverse bias of 5.5 V with minimum background radiation on the diode. For the low-bias region, a study of the reverse current as a function of temperature indiactes that the current transport mechanism is thermal in nature, and that it is dominated by the generation current in the space-charge region of the junction, The target structure is very similar to the silicon diode array vidicon target; the n-type substrate side of the target receives the infrared image, while the array side is scanned by an electron beam. The spectral sensitivity for radiation passing through the n-type substrate of an InAs photodiode is narrow-band nature and can be greatly increased by the use of a heavily doped n^{+} -substrate, which causes the absorption edge to shift to the higher energy. Such an infrared vidicon target structure can be very effective, for it automatically eliminates large amounts of unwanted background radiation without use of a lossy filter. InAs charge-storage photodiodes are also proven to be very, sensitive high-gain infrared, detectors, because of a carrier multiplication gain which results in quantum efficiencies greater than unity. The internal carrier multiplication is an integral part of the charge-storage array diodes in vidicon operation. InAs charge-storage photodiode arrays have been measured, with a demountable electron-beam TV system and preliminary test results have been obtained. Measurement of a line array with electron beam reveal a high sensitivity at a wavelength of 3.25 µ. The results indicate that very sensitive infrared imaging systems using a beam readout technique are realizable.

Comparison of Photomultiplier and Si Photodiode as Detectors in Radiation Pyrometry

Abstract: A performance comparison of the photomultiplier, with type S-20 cathode, and the Si photodiode is performed from the standpoint of noise limited temperature resolution, dynamic temperature range, and potential precision in connection with their use in radiation pyrometry. The analysis demonstrates the superiority of the Si detector working at 1-μm wavelength.

Process for making an optimum high gain bandwidth phototransistor structure

Abstract: THE FABRICATION OF TWO SEMICONDUCTOR STRUCTURES SUCH AS A HIGH SPEED, OPTINUM SENSITIVITY PHOTODIODE AND A MAXIMUM GAIN-BANDWIDTH TRANSISTOR ON THE SAME WAFER IS DESCRIBED. A THIN, LOW RESISTIVITY LAYER IS FORMED ON A HIGHER RESISTIVITY SUBSTRATE AND THE DIODE JUNCTION IS THEN FORMED IN ONE PART OF THE WAFER BY DIFFUSING THE JUNCTIONFORMING REGION THROUGH THE LAYER AND DOWN INTO THE SUBSTRATE. THIS PROVIDES A DIODE OF LOW CAPACITANCE AND OPTIMUM LIGHT SENSITIVITY. THE TRANSISTOR IS THEN FORMED IN ANOTHER PART OF THE SAME WAFER BY FIRST DIFFUSING THE BASE-COLLECTOR JUNCTION INTO THE THIN LAYER FOLLOWED BY A DIFFUSION THEREIN OF THE EMITTER-BASE JUNCTION. THIS DIFFUSION INTO THE LAYER IS VERY SHALLOW AND RESULTS IN A HIGH GAIN-BANDWIDTH TRANSISTOR. THE PHOTODIODE STRUCTURE IS AFFECTED VERY LITTLE BY THE PROCESSING REQUIRED TO FORM THE TRANSISTOR, THUS ALLOWING EACH STRUCTURE TO BE INDEPENDENTLY OPTIMIZED.

Design possibilities for photodiode arrays with integral silicon-gate scan generators

Abstract: A RECENTLY-DESCRIBED single-dimension self-scanning photodiode array has been seminal to a growing number of modified structures for a variety of applications. The MOS shift register, which controls array scanning, has in particular demonstrated considerable versatility and applicability for different array designs. This paper will discuss the tradeoffs in shift register and photodiode structure which set the limits on array performance.

Accurate digital measurement of pulsed laser energy

Abstract: An energy measuring system has been developed using a planar vacuum photodiode as detector with capacitative integration of the photocurrent and subsequent display on a digital voltmeter. The great advantages of this system are that (i) it is small in size and weight at the optical end, (ii) it produces an instantaneous readout, (iii) the readout is digitally expressed directly in millijoules, (iv) the system is independent of ambient light level, (v) simultaneous measurement of power is available and (vi) the operation is automatic. Comparison with a standard calorimeter shows that the system has a consistency of better than 1%.

II Picosecond Laser Pulses

Abstract: Publisher Summary This chapter deals with picosecond light pulses that can be conveniently generated in laser media having wide spectral bandwidths and long fluorescent lifetimes. The availability of optical pulses of such high power and short time duration has aroused considerable interest among military, academic, and industrial researchers. Electrical pulses, having a rise time of less than 10 -10 sec, amplitudes of 60–100 V, and repetition periods as short as 1.5 nsec have been generated by detecting these ultrashort laser pulses with fast photodiode detectors. The application of high-energy, picosecond laser pulses in high temperature plasma experiments, optical radar, optical information processing, spectroscopy, nonlinear optical properties of materials, transient response of quantum systems, radiative lifetime measurements, stimulated scattering, and ultrashort acoustic shock research appears promising.

New Optoelectronic Devices Made of Zinc-Compensated Silicon

Abstract: A brief description is given of the principal physical properties of p- and n-type silicon compensated with zinc. Specific suggestions are made about the possible applications of compensated silicon in new optoelectronic and electronic devices. It is shown that this material can be used in photoresistors, light amplifiers, radiation converters, memory elements, photodiodes, and other devices. The principal parameters of these devices are given. It is concluded that zinc-compensated silicon is a promising optoelectronic material.

Studies of Optical Augmentation With Picosecond Pulses. Picosecond Pulses for Resolution of Optical Elements by Retroreflection

Abstract: : Picosecond optical pulses generated by a neodymium-glass mode- locked laser were employed in laboratory measurements of the retro-reflection from optical surfaces. These measurements were directed at a determination of the minimum separation distance between surfaces which could be resolved using either a photodiode or an image converter camera for detection. A minimum resolvable distance of 7.5 cm was obtained with a photodiode, and the camera yielded a value of 1.5 cm. In addition calculations have been made of the range at which the retroreflection technique may be employed for analyzing optical elements using short pulses. Ranges of several kilometers appear feasible.

Semi-conductive apparatus for detecting light of given flux density levels

Abstract: Apparatus for detecting light having at least a given flux density level and for discriminating between light of said given level and all other low levels of light regardless of their total illumination flux value. The apparatus comprises a PNP silicon conductor sandwich having a front side consisting of a photodiode and a back side consisting of a conventional diode. A battery and resistor are serially connected to the integrated circuit combination, and a signalling current flows through the resistor only when light having at least said given flux density level impinges a target surface of the photodiode.

D.C. coupled impedance reducing circuit

Abstract: Small current signals (0.5 ua and less) such as the output of a photodiode are direct current coupled to a preamplifier which also passes an impedance reducing injection current to a pair of amplifiers. A voltage output proportional to the logarithm of the signal current is produced by passing the amplified current through a log producing junction of a transistor. However, to produce the logarithm function accurately, the injected or impedance reducing current is precisionally removed so that only a very minute portion (one part out of 5000) passes through the log producing junction.

Optical-to-electrical signal transducer apparatus

Abstract: A photosensitive semiconductor array includes a plurality of photodiodes with separate output electrodes and color filters overlaying each photodiode. Each of the photodiodes, when simultaneously exposed to a point source of image bearing multicolored light focused on the photodiode array, responds by producing signals at its output terminals. The size of each photodiode and the filters overlaying same may be altered to change the response thereof. The photodiode array is useful in translating a light beam scanning motion picture film frames into red, green and blue color signals.

Wireless Temperature Measurement of a Sample in Vacuum

Abstract: The temperature of a sample suspended from a microbalance is difficult to measure without interfering with the weighing process. A device is described in which the sample temperature causes a change in frequency of the infrared emitted from a gallium arsenide photodiode. The oscillator unit is mounted in a small hermetically sealed box which in turn is moiunted on the microbalance as part of the sample weight. A thermistor is buried in the sample, attached by fine wires at any convenient distance from the box to minimize circuit thermal sensitivity. Power to operate the oscillator is derived from a silicon solar cell, activated by a light exterior to the chamber. The gallium arsenide cell output can be detected at distances ranging from a few inches to several hundred feet by a suitable photocell. The detected signal is fed into a frequency meter.

An Investigation of Photodiode Response

Abstract: This paper summarizes the basic laws of relaxation for photocarriers separated by a p-n junction. A method is proposed for measuring the parameters of this mechanism and determining its role in the experimentally observed transient processes. A suitable apparatus is described, together with a series of measurements on rectangular silicon photodiodes, and their results.

Question concerning a p-n photodiode in the integrating mode

Abstract: An analysis of the photodiode working in the integrating mode was presented by Chamberlain (1969). His starting formulas are erroneous. A correct expression for the voltage across an illuminated diode is given here. This formula is in agreement with the one obtained by Weckler (1967) for linearly graded junctions.

1/f Noise of Surface-Barrier Diodes

Abstract: A study was made of the 1/f noise of surface-barrier diodes in various circuit configurations. A comparison was made of the noise characteristics of silicon surface-barrier diodes and of conventional germanium and silicon photodiodes. The results of noise measurements under photovoltaic conditions were analyzed on the basis of the fluctuations of the surface recombination velocity. It was found that the surface recombination velocity in“thin” photodiodes could be determined by comparing the noise under the short-circuit and open-circuit (photo-emf) conditions.