Showing papers on "Responsivity published in 1985"

Wavelength‐selective voltage‐tunable photodetector made from multiple quantum wells

Abstract: We show that a pin‐doped multiple quantum well (MQW) diode can be used as a photodetector whose voltage of maximum photocurrent is wavelength dependent. The voltage of maximum photocurrent can be located accurately and related to the wavelength of the incident light, allowing measurements of the wavelength with a precision of 0.03 A=1.2 GHz. This provides a simple, compact, solid‐state device that can be simultaneously used to measure the intensity and wavelength of an optical beam. Furthermore, the device shows high responsivity, low dark current, and fast response.

Non-Equilibrium Devices For Infrared Detection

Abstract: A non-equilibrium mode of operation for semiconductor infrared photodetectors is proposed which will enable their cooling requirements to be substantially reduced. The operating temperature of 3-5 μm band detectors may be raised from - 200K to near ambient, whilst for the 8-12 μm band devices thermoelectric coolers can be considered in place of liquified nitrogen systems. The phenomena of minority carrier exclusion and extraction are utilised in order to maintain the densities of both carrier types well below the near intrinsic, equilibrium values associated with these elevated temperatures, with consequent improvements in responsivity and D.

20 GHz bandwidth InGaAs photodetector for long-wavelength microwave optical links

Abstract: InGaAs photodetectors have been fabricated having a packaged RC plus transit-time-limited bandwidth of 20 GHz and a fibre-coupled responsivity of 0.55 A/W. Using a directly modulated InGaAsP diode laser, the photodetector optical frequency response was measured 3 dB flat to 17 GHz, the bandwidth limit of the laser.

Spectral and temporal characteristics of AlGaAs/GaAs superlattice p-i-n photodetectors

Abstract: Measurements of the spectral and the temporal response of AlGaAs/GaAs p-i-n photodetectors with superlattice intrinsic regions grown by molecular beam epitaxy are reported. The feasibility for high-speed applications is demonstrated by a time constant limited impulse response of 200 ps (full width at half-maximum) when excited near the band edge with 100 ps optical pulses. The theory-predicted and recently verified voltage tunability of the band edge with clearly resolved excitonic resonances was observed. The responsivity was measured to be 0.2 A/W.

Photoconductive HgCdTe Detector Performance with Background Variations

Abstract: The variations of responsivity and ɡ- r noise with background photon flux above 10 16 photons cm −2 sec −1 show strong majority carrier effects for 0.1 eV HgCdTe detectors. The background dependence of Auger lifetime and excess majority and minority carriers densities are sufficient to describe observed phenomena. Excess l/f noise seems related to the minority carrier density resulting in an observed decrease in l/f noise corner with reduced background photon flux.

High responsivity HgCdTe heterojunction photoconductor

Abstract: We present an experimental and theoretical study of n‐type Hg1−xCdxTe photoconductors in which a large band‐gap alloy was grown on top of a smaller band‐gap active region and contacts were made to the larger gap material. The larger band‐gap material causes an energy barrier to holes which decreases the rate at which they reach the high recombination region of the metal‐semiconductor interface. As a result, this heterojunction contact greatly reduces the effects of carrier sweepout on device performance and leads to much higher detector responsivities. Experimental results in a symmetric device with a cutoff wavelength of 7.8 μm at 77 K show responsivities in excess of 106 V/W and detectivities close to the background limited value and nonsaturation of responsivity with bias voltage. In an asymmetric device, in which only one heterojunction contact was used, an order of magnitude increase in responsivity was observed when the heterojunction contact was biased to attract minority carriers, compared with th...

Integrated Zinc oxide-on-silicon tactile-sensor array

Abstract: A 64-element piezoelectric tactile-sensor array, integrated on a silicon chip, has been fabricated and tested. The sensor array consists of 1µm-thick sputtered ZnO piezoelectric capacitors in an 8 × 8 matrix with each sensing element measuring 70 × 70µm2and spaced with a pitch of 70µm. Each sensor element is connected to an on-chip NMOS buffer-amplifier. The measured piezoelectric coefficient d 33 in the ZnO films is 14.4 pCN-1. The measured voltage responsivity (at T=300K) is 5.2 mV/gm with a hysteresis-free linear response for loading to 200 gm.

Absolute response and noise equivalent power of cyclotron resonance‐assisted InSb detectors at submillimeter wavelengths

Abstract: Spectra are presented of the responsivity and noise equivalent power (NEP) of liquid-helium-cooled InSb detectors as a function of magnetic field in the range 20-110 per cm. The measurements are all made using a Fourier transform spectrometer with thermal sources. The results show a discernable peak in the detector response at the conduction electron cyclotron resonance (CCR) frequency for magnetic fields as low as 3 kG. The magnitude of responsivity at the resonance peaks is roughly constant with magnetic field and is comparable to the low-frequency hot-electron bolometer response. The NEP at the peaks is found to be comparable to the best long wavelength results previously reported. For example, NEP = 4.5 x 10 to the 13th W/(square root of Hz) at 4.2 K, 6 kG, and 40 per cm was measured. The InSb CCR will provide a much improved detector for laboratory spectroscopy, as compared with hot electron bolometers, in the 20-100 per cm range.

Design and performance of a SWIR HgCdTe hybrid module for multispectral linear array/landsat applications

Abstract: A modular focal-plane array composed of a SWIR photovoltaic HgCdTe/Si hybrid module has been developed for NASA Earth Resources application. Detector arrays have been fabricated for use in the 1.0-2.5-µm wavelength regime using ion-implanted planar photodiodes formed in liquid-phase epitaxial layers grown on CdZnTe substrates. The resulting diodes have shown R_{0}A_{J} products as high as 2 × 105Ω . cm2at 200 K. The detector design features a gate and a guard structure to reduce leakage current and provide improved optical definition. The multiplexer is a low-noise n-channel direct readout circuit with a 256 : 2 architecture. When the hybrid is operated at 145 K, nonuniformity of responsivity under uniform illumination is less than 8 percent, operability is 99 percent, D* is 82-percent BLIP at 4.7 × 1013ph/cm2. s for a 50-percent quantum efficiency detector, the nonlinearity of the modules is less than 1 percent, and the crosstalk is less than 5 percent.

Effect of Incident Light Illumination Shape on Responsivity of GaAs MESFET Photodetector

Abstract: Photoresponsivity of a GaAs MESFET is investigated. By matching the incident light illumination shape to the electrode shape of the device, an improvement of a factor ~3 in the photoresponsivity was observed. This suggests that the photoresponsivity of GaAs MESFET's is substantially due to a channel current caused by a direct optically-induced modulation of depletion layer.

A wide spectral band photodetector with PtSi/p-Si Schottky-Barrier

Abstract: The photoresponse of a front-illuminated PtSi Schottky-barrier detector is measured in the wavelength range between 0.4 and 5.2μm. In the wavelength range longer than 1.1μm, the detection mechanism is the internal photoemission. On the other hand, the intrinsic mechanism becomes dominant in the wavelength range shorter than 1.1μm. The measured data are in good agreement with values calculated from these two detection mechanisms. The photoresponse depends on the PtSi thickness in both wavelength ranges. For getting a high responsivity, it is important to make a thin uniform metal film. The visible and the thermal image with a PtSi Schottky-barrier wide spectral band imager are also demonstrated.

A monolithic common-collector front-end optical preamplifier

Abstract: A monolithic transimpedance preamplifier has been developed having a common-collector cascode configuration with shunt feedback, using an advanced bipolar IC process. The measured sensitivity was -35.0 dBm at 140 Mbit/s for an error rate of 10-9and a p-in photodiode responsivity of 0.5 A/W.

Optimization Of Indium Antimonide Detectors For Use At Liquid Helium Temperatures

Abstract: Indium Antimonide detectors have been fabricated with characteristics optimized for operation at liquid Helium temperatures. Responsivity and electrical characteristics of these detectors have been measured and are reported here. Results show that no significant loss of responsivity occurs in the three to five micron region, as had been previously reported. Also, a significant reduction in capacitance (factor of 4) has been realized.

Stop-cleaved InGaAsP laser monolithically integrated with a monitoring detector

Abstract: We report the monolithic fabrication of a stop‐cleaved laser with a monitoring detector. Stop‐cleaved, double channel planar buried heterostructure lasers with threshold currents of 57 mA have been obtained emitting at 1.3‐μm wavelength. For the monitoring detector on the same substrate we have estimated a quantum efficiency of 31% from the measured responsivity of 14.4 μA/mW and the theoretical diffraction coupling efficiency.

Charge-injection-device 2×64 element infrared array performance

Abstract: Three 2 x 64 element Si:Bi accumulation-mode charge-injection-device (CID) arrays were tested at low and moderate background to evaluate their usefulness for space-based astronomical observations. Testing was conducted both in the laboratory and in ground-based telescope IR observations. The devices showed an average readout noise level below 200 equivalent electrons, a peak responsivity of 4 A/W, and a noise equivalent power of 3 x 10 to the -17th W/sq rt Hz. This sensitivity compares well with that of nonintegrating discrete extrinsic silicon photoconductors. The array well capacity was significantly smaller than predicted. The measured sensitivity makes extrinsic silicon CID arrays useful for certain astronomical applications. However, their readout efficiency and frequency response represent serious limitations in low-background applications.

Electron discharge device having a narrow range spectral response

Abstract: A so-called "solar-blind" photomultiplier tube includes an envelope having a sidewall and an input faceplate formed from an ultraviolet transmitting filter. A photoemissive cathode is disposed within the envelope for providing photoelectrons in response to radiation incident thereon. The cathode has an intrinsic responsivity extending from the near-ultraviolet portion through the visible portion of the electromagnetic spectrum; however, the filter faceplate transmits only the ultraviolet portion of the spectrum to the photoemissive cathode. The combination of the filter faceplate and the photoemissive cathode therefore limits the tube to a responsivity within the wavelength range of about 300 to less than 400 nanometers.

Detectors For Picosecond Optical Power Measurements

Abstract: There are many features in addition to time resolution that are desirable for a picosecond optical power measurement system. An interdigitated contact, Schottky barrier silicon photodiode coupled to an electro-optic sampler exhibits a rise time better than 22 picoseconds, a quantum efficiency greater than 30%, a uniform responsivity over its receiving aperture, and a usable spectral response to beyond 2 micrometers.

InGaAsP p‐i‐n photodiodes for optical communication at the 1.3‐μm wavelength

Abstract: The preparation and properties of Cd‐diffused p‐n homojunction InGaAsP photodiodes designed specifically for operation at the 1.3‐μm wavelength are described. At a reverse bias of 10 V, the dark current of these diodes was as low as 15 pA. The peak responsivity at 1.3‐μm wavelength was 0.7 A/W. An impulse response (full width at half maximum) of 60 ps and a 3‐dB bandwidth of 5.5 GHz were achieved.

High-Speed Internal Photoemission Detectors Enhanced by Grating Coupling to Surface Plasma Waves

Abstract: The use of gratings to couple optical energy into surface plasma wave (SPW) modes that are confined to a metal-dielectric boundary has been extensively explored [1]. With optimal choices of the grating period and profile, nearly 100% coupling efficiency has been achieved in wavelength ranges where the metal is normally almost totally reflecting. We report the use of this coupling to enhance the quantum efficiency of internal-photoemission detectors in which hot carriers, generated in a metal film by optical absorption, are collected by photoemission over a Schottky barrier into a semiconductor. This class of detectors is of interest as a result of its uniformity, high-speed potential, long wavelength response with binary rather than quaternary III–V compounds, and compatibility with integrated circuit fabrication techniques [2, 3, 4]. For metal-silicide/Si systems, which have been the most thoroughly explored, techniques such as back-illumination and double-pass insulator-metal overlayer structures already provide quite high absorption (> 40%) at infrared wavelengths. Surface texturing has also been used to enhance the responsivity of metal-insulator-metal tunnel junction detectors and of metal-(a-Si)-metal detectors [5,6].

Diffused GaSb photodiode in planar technology

Abstract: For the first tim GaSb planar photodiodes were made by diffusion from a spin-on dopant. First devices show high responsivity over a broad range of wavelengths, low capacitance and medium speed even at zero bias. The rather high reverse currents show trap assisted tunneling. A second trap was determined by low frequency noise measurements.

Performance of charge-injection-device infrared detector arrays at low and moderate backgrounds

Abstract: Three 2 x 64 element charge injection device infrared detector arrays were tested at low and moderate background to evaluate their usefulness for space based astronomical observations Testing was conducted both in the laboratory and in ground based telescope observations The devices showed an average readout noise level below 200 equivalent electrons, a peak responsivity of 4 A/W, and a noise equivalent power of 3x10 sq root of W/Hz Array well capacity was measured to be significantly smaller than predicted The measured sensitivity, which compares well with that of nonintegrating discrete extrinsic silicon photoconductors, shows these arrays to be useful for certain astronomical observations However, the measured readout efficiency and frequency response represent serious limitations in low background applications

Theory of deep level trap effects on generation‐recombination noise in HgCdTe photoconductors

Abstract: We present a theory of the effect of deep level centers on the generation‐recombination (g‐r) noise and responsivity of an intrinsic photoconductor. The deep level centers can influence the g‐r noise and responsivity in three main ways: (i) they can shorten the bulk carrier lifetime by Shockley–Read–Hall recombination; (ii) for some values of the capture cross sections, deep level densities, and temperature, the deep levels can trap a significant fraction of the photogenerated minority carriers. This trapping reduces the effective minority carrier mobility and diffusivity and thus reduces the effect of carrier sweep out on both g‐r noise and responsivity; (iii) the deep level centers add a new thermal noise source, which results from fluctuations between bound and free carriers. The strength of this new noise source decreases with decreasing temperature at a slower rate than band‐to‐band thermal g‐r noise. Calculations have been performed for a X=0.21, n‐type Hg1−xCdxTe photoconductor using the parameters...

Short wavelength responsivity improvement and long wavelength responsivity degradation in photodiodes as a result of gamma irradiation

Abstract: Changes in surface and bulk properties of United Detector Technology pin-05D photodiodes as a result of 1.3 Mrad gamma irradiation are compared. As suspected by previous investigators but not verified until now, changes in surface properties are seen experimentally to significantly alter overall device characteristics. Changes in device properties include increases in surface conductivity, improved quantum efficiency at visible wavelengths, decreased dark current at very low reverse bias, decreased diode ideality factor, decreased infrared response, and decreased minority carrier lifetime. The first four results are new and permit differentiation between surface and bulk effects. A model consistent with all of these measurements is presented to explain the changes. The model is based upon gamma ray photodesorption of surface impurities.

Time-resolved photorefractive four-wave mixing in semi-insulating semiconductors

Abstract: High-mobility semiconductors including InP1 and GaAs1,2 offer several advantages for photorefractive image processing: (1) recording sensitivities comparable with those of oxide photorefractors such as LiNbO3, BaTiO3, and Bi12SiO20; (2) near-infrared responsivity, the spectral region of importance for semiconductor lasers, and optical communications; (3) high mobility allowing fast photorefractive responses ranging from nanoseconds to milliseconds; (4) optical and electrical properties that can be tailored by doping.

Photoconduction in Thin-Film Transistors Fabricated from Lasercrystallized Silicon on Fused Quartz

Abstract: Photoconduction with optical gain in excess of 3000 is achieved in depletion-mode MOSFETs fabricated from laser-crystallized silicon thin-films on fused quartz. Devices operated with a reverse gate bias show responsivity of ≥ 300 Amp/Watt for radiation in the visible spectrum and dynamic range of > 106. This process occurs by spatial separation of photogenerated electron-hole pairs across a p-n junction in the device body, collection of holes in the floating substrate, and conduction of electrons in a buried channel in the bulk of the nearly defect-free silicon film. This study explores the influence of channel dopant profile on the photoconduction process and the latitude for optimized photodetector performance. The effect of post-crystallization residual structural defects on performance uniformity is also evaluated.