Showing papers on "Responsivity published in 1983"

A new infrared detector using electron emission from multiple quantum wells

Abstract: A new type of infrared photodetector using free electron absorption in a heavily doped GaAs/GaAlAs quantum well structure has been demonstrated. Preliminary results indicate a strong response in the near infrared with a responsivity conservatively estimated at 200 A/W. The structure can potentially be tailored during fabrication for use in several infrared bands of interest, including the 3 to 5 micron band and the 8 to 10 micron band.

Performance and materials aspects of Ge:Be photoconductors

Abstract: Ge:Be photoconductors were developed for low photon background applications in the 30 to 50 MM wavelength region. These detectors provide higher responsivity and lower noise equivalent power (NEP) than the Ge:Ga detectors currently operating in this wavelength range. Beryllium doped single crystals were grown by the Czochralski method from a carbon susceptor under a vacuum of approx. one million torr. An optimum detective quantum efficiency of 46% at a background flux of 1.5 x 10 to the 8th power photons/second (7 x 10 to the 13th power W) was reported. Ge:Be detector performance is strongly influenced by the absolute concentrations and the concentration ratio of residual shallow donors and shallow acceptors.

High-speed GaAlAs/GaAs p-i-n photodiode on a semi-insulating GaAs substrate

Abstract: A high-speed, high-responsivity GaAlAs/GaAs p-i-n photodiode has been fabricated on a GaAs semi-insulating substrate. The 75-µm-diam photodiode has a 3-dB bandwidth of 2.5 GHz and responsivity of 0.45 A/W at 8400 A (external quantum efficiency of 65%). The diode is suitable for monolithic integration with other optoelectronic devices.

Theory of generation‐recombination noise and responsitivity in overlap structure photoconductors

Abstract: A rigorous theory of both responsitivity and generation‐recombination noise in overlap structure photoconductors is presented. Because generation‐recombination noise dominates under typical operating conditions, these results combine to give the detectivity D*. It is found that both responsivity and D* can be improved by use of the overlap structure. The dependence of the optimum device geometry on the operating conditions, such as bias conditions, and on the parameter to be maximized (e.g., responsivity or D*), is derived. Symmetric and asymmetric overlap structure are compared, and it is found that, except at very small bias fields, an asymmetric structure gives the largest improvement in both the responsivity and D*. Both responsivity and noise voltage are found to roll off at lower frequencies for the overlap structure than for the standard design, but become equal to the standard design values at high frequencies. Numerical results for x≊0.21 HgCdTe detectors are presented. Using an asymmetrical over...

Electromagnetic radiation detector

Abstract: The electromagnetic radiation sensitive detector comprises a substrate (10), a first layer (12) on the substrate of radiation sensitive semiconductor material of a given conductivity type and having a first energy bandgap, at least one ohmic contact (16) providing electrical communication with the first layer, and a second layer (14) of semiconductor material of the same conductivity type as the first layer but having an energy bandgap greater than that of the first layer, the second layer being located on the first layer (12) beneath the or each contact (16) to which minority carriers are attracted from the first layer to enhance the responsivity of the detector

The spectral response of BSF silicon solar cells fabricated through masked ion implantation

Abstract: The work presents the main peculiarities of the spectral response of back-surface-field (BSF) silicon solar cells fabricated through masked ion implantation of the n+-p junction. The emphasis is on the shift of maximum responsivity toward the visible spectrum and on the large bandwidth of these n+-p-p+ optical sensors. The dependence of these parameters on technological parameters are outlined in the communication.

A PtSi Schottky-barrier infrared MOS area imager with large fill factor

Abstract: A 64 × 64-element silicon monolithic infrared MOS area imager (IR-MOS) with platinum silicide Schottky barrier (PtSi S.B.) detectors has been developed. Using MOS X-Y address circuitry, the fill facter of the device increased to 56 percent without degradation of the dynamic range. The dynamic range was 48 dB The responsivity was 2.9\times10^{8} V/W at 1000 K and the sensitivity was 10.5 mV/K at 300 K. The performance of the IR-MOS was sufficient to obtain a thermal image in the range of the 3 to 5 µm atmospheric window without any electrical compensation of the imaged signal.

Wavelength-discriminating photodetector for lightwave systems

Abstract: We demonstrate that a dual-wavelength photodetector can be used to determine simultaneously the wavelength and the power level of a lightwave signal. The signal wavelength is determined by monitoring the ratio of the two outputs from this photodetector at the crossover of its responsivity curves; the signal level is determined from the sum of the two outputs. Possible applications for this type of photodetector include mode-control of single-frequency injection lasers, direct demodulation for lightwave systems utilising frequency-shift-keyed transmission, wavelength-division multiplexing and optical logic.

Pyroelectric measurements of (1‐reflectivity) in the visible for metallic films

Abstract: The use of pyroelectric sensors to measure the optical properties of thin metallic films is reported. New results on the pyroelectric responsivity versus temperature in ferroelectric Pb5Ge3O11 are reported.

Focal Plane Spatial Response And Modulation Transfer Function (MTF) Measurements Using A Computer-Aided Flying Spot Scanner

Abstract: In the measurement and characterization of the performance of infrared and visible focal plane arrays, the determination of the detailed spatial response of individual detectors as well as the entire array can be extremely important in many electro-optic sensor applica­ tions such as the detection of targets in the presence of clutter and passive acquisition and tracking. This paper describes a computer-controlled flying spot scanning technique for the measurement of detailed focal plane detector responses as well as detector-to-detector cross talk and spurious responses. The technique uses a computer-controlled flying spot scanner and online data processing. A simple deconvolution is used to remove the known temporal responses of the detector and electronics followed by a two-dimensional decorrela- tion of the blur spot from output signal to obtain focal plane spatial response. As a natural result of this process the individual detector MTFs can be obtained. This technique has been implemented in a low-background focal plane test facility, which is also described. Several examples of actual test data are shown to demonstrate the use of this spot-scanning facility and its utility as a diagnostic tool.IntroductionIn the design and development of sophisticated electro-optic sensors for infrared (IR) and visible applications, both detailed focal plane performance characterizations and end- to-end simulations using complex computer programs are essential to the design of the sen­ sor and the optimization of its performance for a given range of scenarios and operating conditions. In earlier papers we have described our computer-aided facilities for detailed testing and characterization of infrared and visible focal plane arrays1' 2' 3 and our low- background brassboard test facility designed specifically to evaluate the end-to-end per­ formance of both scanning and staring IR sensors over a wide range operating condi­ tions.4 The brassboard test facility presents a wide range of target and background sig­ nals and image scenes to infrared focal planes which are interfaced a dedicated online minicomputer. The minicomputer acts as a programmable realtime or near-realtime signal processor through which the sensor performance can be measured and signal processing algor­ ithms can be evaluated using real signals from the focal plane detectors. This paper describes a technique for measurement of the detailed spatial responses of individual detectors and detector arrays using these facilities.In the analysis and characterization of sensors, important assumptions are made about the spatial responsivity variation of the individual detectors. Often in performance analyses (such as tracking performance analysis), the detector responsivity is assumed to be flat over the area of detector and zero outside. For some detectors, however, actual responsivity deviates significantly from this hypothetical shape. The boundaries may com­ prise a significant portion of the detector real estate. The responsivity in central area of the detector may not be flat but may have significant nonuniformities. The actual shape of the detector responsivity functions may have significant effects on the results of performance analyses for both individual detectors and focal plane arrays.In many cases, such as a fine tracker, sensor performance requirements dictate that more accurate and detailed estimate of the detector responsivity function must be obtained and utilized in further signal processing. A powerful technique for obtaining the detailed spatial responsivity function of individual detectors and focal plane arrays uses a computer-controlled flying spot scanner. However, because the blur spot of a typical spot- scan system is of the same order magnitude as detector cell size, true respon­ sivity shape cannot be obtained by a simple point-by-point spatial measurement without accounting for and removing the effect of finite blur-spot size and shape. In order to do this we utilize a recently developed two-dimensional decorrelation technique^ to obtain the detector responsivity function from detector spot-scan data obtained in our test facil­ ities. Furthermore, the modulation transfer function (MTF) of individual detectors (the magnitude of the response function in the spatial frequency domain) is also obtained.41

Characterisation of electrical and optical base controlled switching in the V-groove isolated punch through mode mist

Abstract: The base controlled switching characteristic of the isolated, punch through mode metal-insulator (tunnel)-silicon thyristor is examined under various base inputs. It is shown that an excitation threshold and sensitivity are sufficient to characterise the electrical and optical base controlled switching modes. A simple model is presented which adequately explains the observed switching characteristics for both electrical and optical excitations. Furthermore for the optical case, the responsivity is derived and measured in order to provide a basis for comparison with existing photodetectors.

The optimum of a thin pyroelectric film on a substrate

Abstract: A series of optimum operating conditions as well as the corresponding noise equivalent power NEP and responsivity expressions for a pyroelectric film on a substrate have been derived by use of the one dimensional heat conduction theory. It is indicated that good quality substrate-attached pyroelectric detectors can be designed according to the derived optimum equations.

Noise and responsivity of commercial p+n Ge avalanche photodiodes

Abstract: Commercial p+n Ge APD samples from two manufacturers are shown to have comparable noise and responsivity, characterised by a quantum efficiency at 1.3 ?m wavelength of 0.7?0.75, and a bulk leakage current density at 20 C of 2?3×10?4 A cm?2 before avalanche multiplication. Surface uniformity of avalanche gain is much better than on earlier n+p devices of the same diameter (100 ?m).

A new-structure LiTaO3 pyroelectric infrared detector

Abstract: A LiTaO3 pyroelectric infrared detector with a new type of structure has been developed.The detective material is supported on an electric conductor by a special conductive adhesive which possesses low thermal conduction.In the fabrication process of the detector, the pyroelectric material is not handled in the form of thin chips, as in the conventional fabrication process. The detector is particularly suited to mass production, and should be able to be manufactured more economically than conventional pyroelectric detectors.The voltage responsivity and the specific detectivity D* (500, 10, 1) of the new type pyroelectric detector are nearly 300 V/W at 10 Hz and 2 × 108 cm√Hz/W, respectively.The pyroelectric responsitivity and D* of this new-type pyroelectric detector are calculated theoretically as a function of the thickness of the pyroelectric element, and the thickness dependence of the responsivity and D* are experimentally confirmed. The theoretical calculation has been shown to be in agreement with ...

Revised broadband-filter method for spectral responsivity measurements

Abstract: This paper revises the broadband-filter method originally proposed by Wyszecki to evaluate the relative spectral responsivity of photodetectors The new mathematical procedure consists of representing the responsivity curve by a spline function to reduce the number of free parameters and to preserve the approximation accuracy Consequently, performance of the calculated spectral responsivity vs experimental errors turns out to be satisfactory Extended simulated examples show the capabilities of this new approach

Monolithic Schottky diode imaging arrays at 94 GHz

Abstract: Monolithic GaAs Schottky diode imaging arrays have been demonstrated at 69 and 94 GHz. In the 94 GHz experiments, the diodes are fabricated by a self-aligning technique on semi-insulating GaAs and are isolated by a combination of a mesa-etch process and proton-bombardment. The series resistance is 20 ω and the estimated capacitance is 15–20 fF. The antennas are planar bow-ties, and power is coupled in through a quartz lens placed on the back of the GaAs substrate. The wafer is lapped to 90 μm thick to eliminate losses to substrate modes. The measured system responsivity is 330 V/W. The 69 GHz diodes are made by a non-self-aligned process, and a silicon substrate lens is used.

1.5 GHz operation of an AlxGa1-xAs/GaAs modulation-doped photoconductive detector

Abstract: We demonstrate a planar AlxGa1-xAs/GaAs modulation-doped photoconductive detector operating at frequencies up to 1.5 GHz. This detector exhibits a peak responsivity of 2 A/W at these operating conditions, which corresponds to a gain of 3. We found that the peak responsivity increased with reduced pulse repetition rates, reaching 5 A/W at 1 MHz. We also measured the noise power at 800 MHz. This investigation suggests that the detector can be useful for shortwavelength (λ = 0.82 μm) giga-bit-rate integrated photoreceiver applications.

Photoconductive detector bias

Abstract: It is a problem extracting the photosignal component from detector output, to the exclusion of pedestal bias response. To overcome this, a time varying bias signal is applied to the detector. The duration of the time varying bias signal, or if a periodic signal, the signal period, is chosen as long compared to photocarrier lifetime and the signal amplitude is large enough to range over a non-linear portion of the responsivity characteristic of each element. The bias signal contains a d.c. component so that the bias signal ranges about a point of operation-a point of asymmetry lying on the responsivity characteristic. The photosignal component of the output signal may be removed by time averaging or by harmonic separation. Alternatively the alternating component of the bias signal may be amplitude modulated at a lower frequency, and the photosignal component extracted by detection of demodulated signal.

Microwave mixing and direct detection using SIS and SIS' quasiparticle tunnel junctions

Abstract: Quasiparticle mixers have shown strong quantum effects, conversion gain, and noise levels approaching the quantum limit, but only in tunnel junctions with very low sub-gap "leakage" conductance. It has been suggested that SIS' tunnel junctions, made from two different conductors with unequal gaps, will function as high gain mixers since the dynamic conductance below the gap is negative. We report results of the first SIS' mixing and direct detection experiments. At 36 GHz, a conversion efficiency of -4 dB with a noise temperature of 33 K (SSB) has been obtained. A novel gain mechanism for SIS' direct detectors is predicted. A direct detector responsivity of 250 A/W was measured. We compare our results to quantum theory models. In addition, we demonstrate quasiparticle harmonic mixing of a 36 GHz signal with an 18 GHz local oscillator in tin SIS junctions. Harmonic mixers can have important advantages at high microwave frequencies where insufficient local oscillator power is available.

A novel GaInAs/GaAs Heterostructure Interdigital Photodetector (HIP) Using Lattice Mismatched Epitaxial Layers

Abstract: Planar high-speed interdigital photoconductive detectors have been fabricated on MOCVD-grown GaInAs/GaAs heterostructures. The small intentional lattice mismatch at the GaInAs/GaAs interface allows a controlled surface recombination velocity which decreases the effective lifetime of minority carriers without significant active layer mobility degradation. The InGaAs detectors have the following characteristics: bandgap of ~ 1.25 eV; rise times of < 25 psec; fall times ~ 50-100 psec; FWHM < 45 psec; high speed responsivity ~0.3 A/W; 2-300 nA leakage current at 5-10 V operating voltages and flat analog response to ~ 15 GHz.

Photoconductive detectors with bias

Abstract: An alternating bias is supplied to a modified photoconductive detector (1) and photosignal extracted from each detector element (2). This extraction may be performed using an integrator (11) to produce dc signal output, or alternatively by using a high-pass filter or phase-sensitive detector to extract photosignal at an harmonic of the bias frequency. The detector (1) used is provided with elements (2) that have a responsivity that is a different function of bias amplitude for each polarity. The detector element (2) may be shaped with variation in width or depth, to produce this differential responsivity. Alternatively element bias contacts (3, 5) may be of different width to produce field gradient and differential responsivity. It is advantageous to obscure a part of each element area (2) by including an opaque mask.

Testing of an Image Intensifier Tube For Astronomical Applications

Abstract: The single state image intensifier tube VARO 4215 is tested for dark background, polarization responsivity and surface responsivity.