Showing papers on "Responsivity published in 1979"

Automatic responsivity compensator in an IR imaging system

Abstract: An automatic responsivity compensator for correcting video output signals om a CCD multiplexer in a cryogenic dewar in IR imaging systems wherein the CCD multiplexer must operate with fixed gain inputs from a plurality of linear detector channels. The automatic responsivity compensator is comprised of a signal reference that is normalized with what the output voltage should be when looking at a fixed temperature source in the field of view of the detectors and which further provides a voltage reference for automatic gain adjustment for each detector channel to normalize and equalize the responsivity of the detectors. The automatic responsivity compensator may be either a feedback system as a direct gain control means of a controllable gain amplifier or may be a feedback system operating on the output from a constant gain amplifier wherein either feedback system equalizes the responsivity of the detectors.

Silicon p-n junction photodiodes sensitive to ultraviolet radiation

Abstract: Experimental studies on a silicon photodiode have been carried out to achieve the performance characteristics required for applications such as spectroscopic measurements Sheet resistance was applied as a control parameter for diffusion to obtain a shallow junction less than 1 µm in depth For high ultraviolet responsivity, the diffusion layer, in which a built-in field is induced by the impurity gradient, was optimized for values of the sheet resistance of about 800-2000 Ω/□ The device responded in the wavelength range of 200-1000 nm,and had a responsivity of 0065 A/W at 200 nm In order to reduce influence of stray light in spectroscopic measurements, two types of photodiodes were fabricated with photoresponse reduced in the long-wavelength portion A p+-n-p+device was found preferable to a p+-n-n+device And the device structure with an extended electrode was desirable for high, reliable performance

Low-Level Radiation Effects in Extrinsic Infrared Detectors

Abstract: Experimental data are presented on the effect of gamma irradiation at low dose levels of 10 Rads or less on the responsivity of arsenic-doped extrinsic IR detectors under operating conditions at 4.3 to 12°K. The observed large changes in responsivity under irradiation, and the subsequent transient behavior during a period of less than 1 minute immediately after the radiation is turned off, are strongly dependent on temperature, bias voltage, and IR flux level. The net effect following irradiation is always a responsivity increase; however, under some conditions, the increase can be preceded by a decrease. The responsivity change relaxes slowly, requiring more than one day for complete recovery of the detector to its pre-irradiation condition. The effects anneal rapidly at temperatures over 20°K. The observed phenomena can be explained by radiation-induced changes in the charge state of the levels associated with the majority IR-active dopant and the compensating impurities. The complex dependence of the responsivity changes on the operating conditions is explained in terms of competing processes involved in capture, recombination, and sweepout of radiation-generated electrons and holes. The physical mechanisms and a qualitative model offering a possible explanation of the effect of temperature, bias, and IR flux level are discussed.

Photon Drag Detection

Abstract: Although photon drag was first observed ten years ago [1] [2] detectors utilizing this effect have been largely confined to CO 2 laser wavelengths. Commercially available detectors are calibrated for 10.6 μm and although they can be used at other wavelengths various pitfalls can arise. Figure 1 shows the voltage responsivity of a typical p-type germanium detector between 2.5 and 13 μm. It is disconcerting to find that not only does the responsivity vary rapidly with wavelength, but the sign of the signal changes five times.

Restoration of high infrared sensitivity in extrinsic silicon detectors

Abstract: A method and apparatus for removing heavy metal impurities such as gold, silver, nickel and copper from a crystalline substrate is described incorporating a damaged crystalline layer which may be formed by excessive doping to trap or getter heavy metal impurities to enhance the majority carrier lifetime of the detector material. The invention overcomes the problem of degraded responsivity in radiant energy crystalline detectors after high temperature processing, in excess of 900° C., which permits surface contaminants such as gold, silver, nickel and copper to diffuse through the detector material raising the net donor density.

Infrared focal plane with automatic responsivity control using photodetector bias modulation

Abstract: Automatic responsivity control for an array of infrared photodetectors is provided without additional hardware such as a beam chopper or a reference object of known irradiance. The requisite modulated reference signal is provided instead by uniformly modulating the bias voltage applied to each of the plurality of photodetectors in the array. Photodetectors having different responsivities respond to the same bias modulation differently to produce a superimposed sinusoidal component in the photodetector output current which is used to compensate for differences in responsivities of the individual photodetectors. For this purpose, an automatic responsivity control circuit selects the superimposed sinusoidal component from the photodetector output current corresponding to the frequency of the reference signal modulating the bias voltage, and compares the amplitude of the selected sinusoidal component with a reference level to adjust the amplification at the photodetector output in accordance with this comparison, so that the amplified outputs from the plurality of photodetectors respond uniformly to the sinusoidal reference signal applied as a bias voltage to the photodetectors.

Calibration of radiation detectors in the VUV using a wall-stabilized Ar-cascade arc

Abstract: A VUV calibration facility is described By means of this equipment, measurement of the responsivity of radiation detectors in the spectral range from 90 nm to 250 nm is possible The measuring method makes use of a wall-stabilized Ar-cascade arc as a standard radiator, and by measuring the spectral transmittance of the optical arrangement, the monochromatic radiant flux, which reaches the detector or the detector system, can be given The spectrum of the Ar arc in particular is investigated in the lambda < 125-nm spectral range

Responsivity and noise characterisation of ge avalanche photodiode throughout wavelength range 1.1–1.7 μm

Abstract: Mixed carrier injection in a commercial n+-p germaniun a.p.d. causes the excess multiplication noise to be wavelength dependent, with averaged k-values of around unity. The quantum efficiency is 70% between 1.1 and 1.5 μm, and the unmultiplied bulk leakage current density is estimated to be 3.5×10-4 A cm-2

A new sensitive microwave bolometer heterodyne receiver

Abstract: Some narrow‐gap mixed crystal semiconductors show a magnetic field induced transport anomaly at low temperatures. The anomaly is accompanied by a transition from a low to a high resistivity state, which in turn causes a strongly nonlinear I‐V characteristic. We have investigated microwave mixing near such a phase transition in n‐type Hg0.8Cd0.2Te with a frequency of 37 GHz at 1.5 K and in magnetic fields up to 8.5 T. The sensitivity characteristic was measured and the responsivity determined to be about 15 times higher than that of a hot‐carrier InSb bolometer. The time resolution of this new bolometer (=10−7 s) was slightly better than in InSb.

Ultraviolet photoconductive detectors in Zn3P2

Abstract: Photoconductive detectors with relatively flat response to wavelengths as short as 2500 A have been fabricated in thin films of zinc phosphide deposited by the close-space-transport method on to mica substrates. Responsivity at 2527 A was 0.13 A/W.

Performance Efficiency Of InSb Charge Injection Devices (CID)

Abstract: This paper describes the factors governing the Performance Efficiency (PE) of Indium Antimonide Charge Injection Devices (CID) arrays. Factors influencing PE in both line and area arrays are considered and compared to experimental results. An important factor re-lates to the signal charge loss of a dual gate array operating in the charge sharing mode (CSM). The chief advantages of the CSM are that it overcomes charge transfer problems that might be present in practical arrays, and it is believed to be radiation damage resistant. The chief limitation is that only the charge residing under the sensing gate of the dual gate site is read out. This loss can be lessened by designing the sensing gate to be a large fraction of the total storage area. Performance data of lx32, lx64 line arrays, 24x16 and 32x32 dual gate area arrays are presented. Line arrays FE up to 56 percent, responsivity variation below 10 percent, and D* of about 3x1011 cm HZ½/watt have been measured.© (1979) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

PIN photodetector under transient conditions: Simulation and experiments

Abstract: An exact simulation of a Silicon PIN photodetector with transient light excitation is presented. The photodetector under consideration is designed to have good responsivity and fast response time in the wavelength range 0.6–0.95 μm which is of interest in fiber optic communication systems driven by GaAs and AlGaAs light sources. The photocurrent transient is computed for step and impulse light excitation using various values of reverse voltage, intrinsic layer thickness and doping. Good agreement is obtained between calculated and experimental waveforms.

SIS Quasiparticle Junctions As Microwave Photon Detectors

Abstract: : The strong nonlinearity of the quasiparticle tunneling current in superconductor-insulator-superconductor junctions near the full gap voltage 2 Delta/e can be used for direct detection of microwave signals Measurements at 36 GHz yielded a current responsivity of 3,5000 A/W, which is within a factor of 2 of the quantum limited value e/h-bar omega The measured NEP of 26 + or - 08 x 10 to the -16th power W/sq-rt Hz is the lowest value reported to date and can probably be improved significantly The experimental results are compared with both the standard classical analysis and photon assisted tunneling theory (Author)

A simple millimeter wave glow discharge detector assembly

Abstract: A waveguide mount for a millimetre wave glow discharge detector is described. The mount design is characterised by a simple tuning mechanism permitted by the unique properties of the glow discharge detector. Results of responsivity and signal-to-noise measurements at 70 GHz are presented and compared with a conventional millimetre wave crystal detector.

InAsSb hybrid imager evaluation

Abstract: Current research on infrared hybrid focal planes is directed toward devices in which detection occurs in a p-n junction formed in an intrinsic narrow energy bandgap semiconductor, and signal processing is accomplished in a Si CCD multiplexer which is electrically interfaced to the detector array. A hybrid array such as this, where the detector format is a 32 × 32 matrix, has been fabricated. The active material is backside-illuminated InAsSb which has been planar processed and fully passivated. The cutoff wavelength is 4.0 µm at the operating temperature of 77K. The CCD is four phase with a two level polysilicon gate structure. The signal input is via direct injection with an option for dc suppression. Operation of the focal plane in a staring mode that uses dc suppression is discussed. Data derived from the video output is presented; this includes responsivity and detectivity. Off focal plane non-uniformity compensation is also discussed. Displays of thermal images utilizing processed data from the hybrid focal plane array will be shown.

Evaluation Of Silicon Diode Arrays For The High-Resolution Spectrograph (HRS) Digicon

Abstract: Diode arrays fabricated by three companies have been evaluated for use in the HRS Digicon. The goal has been to optimize design and performance in the pulse counting mode. The arrays have been characterized using both photon and electron inputs. Responsivity, optical crosstalk, and a new phenomena "lead response" have been measured as a function of wavelength between 400 and 800 nm. Using pulse height analysis techniques, arrays were characterized with respect to noise and signal-to-noise ratio using low-level electron input. An attempt has been made to establish a correlation between non-intensified (photon input) and intensified (electron input) performance.