Showing papers on "Photodiode published in 1982"

Enhancement of electron impact ionization in a superlattice: A new avalanche photodiode with a large ionization rate ratio

Abstract: The first superlattice avalanche photodiode (APD) is reported. The high field region of this p‐i‐n structure consists of 50 alternating Al0.45Ga0.55As (550 A) and GaAs (450 A) layers. A large ionization rate ratio has been measured in the field range (2.1–2.7)×105 V/cm, with α/β≃10 at a gain of 10 giving a McIntyre noise factor Fn = 3. The ionization rate ratio enhancement with respect to bulk GaAs and AlGaAs is attributed to the large difference in the band edge discontinuities for electrons and holes at the heterojunction interfaces. The superlattice APD is a new device concept which can be used to develop low noise APD’s in a variety of III‐V materials including long wavelength 1.3–1.6‐μm semiconductors.

Multichannel grazing-incidence spectrometer for plasma impurity diagnosis: SPRED

Abstract: A compact vacuum ultraviolet spectrometer system has been developed to provide time-resolved impurity spectra from tokamak plasmas. Two interchangeable aberration-corrected toroidal diffraction gratings with flat focal fields provide simultaneous coverage over the ranges 100–1100 A or 160–1700 A. The detector is an intensified self-scanning photodiode array. Spectral resolution is 2 A with the higher dispersion grating. Minimum readout time for a full spectrum is 20 msec, but up to seven individual spectral lines can be measured with a 1-msec time resolution. The sensitivity of the system is comparable with that of a conventional grazing-incidence monochromator.

No image lag photodiode structure in the interline CCD image sensor

Abstract: An undesirable image lag with a long time constant was found in the interline CCD image sensor having N+P-junction photodiode (PD). This paper clarifies the image lag mechanism and proposes a new photodiode structure having no image lag. The image lag measurement method and the experimental results are also given. The experimental results quantitatively agreed with the analytical model, in which signal electrons are assumed to be transferred from the PD to the vertical CCD as a small subthreshold current. To eliminate the image lag, a P+NP-structure PD with low donor concentration was proposed, where all the signal electrons can be quickly transferred before the subthreshold condition begins. As a result, the decay lag values of the 1st and the 2nd fields were reduced to half and the decay lags after the 3rd field were not observed.

Optical response time of In0.53Ga0.47As/InP avalanche photodiodes

Abstract: Heterojunction In0.53Ga0.47As/InP avalanche photodiodes have recently been observed to have a response to long‐wavelength optical pulses which contains both fast and slow components. We present evidence that the slow response is limited by charge pile‐up at the semiconductor heterointerface. We find that the speed of response depends on the degree of compositional grading in the heterointerface region. The response time can be significantly reduced for compositional grading lengths of greater than 600 A depending on the doping and depletion region width in the In0.53Ga0.47As layer.

Background and temperature dependent current‐voltage characteristics of HgCdTe photodiodes

Abstract: The zero bias resistance‐area products and current‐voltage (I‐V) characteristics as a function of temperature and infrared background radiation have been measured for HgCdTe photodiode samples with cutoff wavelengths near 9 μm at 80 K. A model is presented to account for the background and temperature dependence of the data. It is found that the reverse I‐V curve shapes and magnitudes may be estimated as a function of both background and temperature by superposition of the total current from optical generation, thermal diffusion, and depletion region generation‐recombination centers. The influence of background radiation was found to create an exceptionally linear reverse I‐V characteristic that can be easily distinguished from other current generation mechanisms, and can be modeled by application of existing theory to HgCdTe photodiodes.

A Proposed Hydrogenation/Nitridization Passivation Mechanism for GaAs and Other III–V Semiconductor Devices, Including InGaAs Long Wavelength Photodetectors

Abstract: A surface passivation method for , with possible extensions to and , is proposed. For , a correlation between recent device work (on solar cells, field effect transistors, MOS devices, and photodiodes) and the experimental Ga‐As‐O phase diagram provides strong evidence of the role of elemental surface or interface arsenic or arsenic oxide in device performance degradation. On this basis, a hydrogenation/nitridization passivation technique is proposed. The reactions to remove surface As and are The surfaces may be plasma coated in the same chamber with a wide bandgap nitride (e.g., ) for passivation and to tie up any elemental Ga. The hydrogenation and nitridization steps may be simultaneous if an ammonia plasma is used. A final layer for long‐term surface protection is recommended. Recent experimental data on surface treatments support this passivation mechanism. The extension to (for long wavelength optical detectors) is by thermochemical calculations supported by recent parallel measurements of the In‐Ga‐As‐O phase diagram. Note the conductive indium oxide must also be removed, as by the reaction

The graded bandgap multilayer avalanche photodiode: A new low-noise detector

Abstract: We propose a new multistage avalanche photodiode for low-noise optical detection. In each stage, the ionization energy is provided by a heterointerface conduction-band step. Thus, ideally, only electrons cause ionization, and the device mimics a photomultiplier. This detector has intrinsically lower noise and lower operating voltage than conventional avalanche detectors. Designs for 1.3 µm fiber optic systems are presented and possible realizations using molecular beam epitaxy discussed.

Interline CCD image sensor with an anti blooming structure

Abstract: THE APPLICATION OF AN overflow drain and barrier positioned beside the photosensitive area? has made it possible to suppress blooming of CCD image sensors. However, this method was found to sacrifice photosensitivity and dynamic range. This paper will describe an interline CCD sensor where the vertical overflow drain is positioned under, rather than beside the photodiode. Thus the cell area can now be used effectively for photoelectron generation and storage, and increased photosensitivity and dynamic range can be maintained. Furthermore, this technique eliminates the blooming phenomenon.

Automatic brightness control apparatus

Abstract: Automatic brightness control apparatus for providing real time control of the brightness of various types of displays while also providing ambient light compensation is disclosed which includes a photodiode for providing a current proportional to the ambient light level. Amplifiers, together with a load, change the photodiode current to a control voltage indicating the level of ambient light. The control voltage is provided as a reference input to a voltage comparator. The other input to the voltage comparator is the output of a free running ramp oscillator. The pulse width modulated logic signal comprising the output of the voltage comparator is provided as the input for an output driver whose pulse stream output is used to control the brightness of the designated display. The duty cycle of the pulse stream output varies with the ambient light level. Several logic gates are added to the free running ramp oscillator to provide synchronization capability and assure that the ramp output waveform of the ramp oscillator will always begin with an incoming synch pulse. The automatic brightness control apparatus is packaged as a monolithic integrated circuit on a single silicon chip which is housed in a clear plastic 8 pin DIP.

Heterojunction phototransistors for long‐wavelength optical receivers

Abstract: We demonstrate by measurement and analysis that previously reported InP/InGaAs heterojunction phototransistors are promising photodetectors for long‐wavelength optical receivers. The gain characteristics of these devices are shown to reflect the benefit of a wide band‐gap emitter as well as the effects of recombination centers near the base‐emitter heterojunction. In order to analyze the noise characteristics we derive a model which accounts for the three principal noise sources: the shot noise of the base current, the shot noise of the collector current, and the thermal noise of the load resistor. Using this model and experimental device parameters, we calculate the sensitivity of an optical receiver which utilizes a heterojunction phototransistor. This calculation indicates that the performance of this monolithic device can be as good as or exceed that of a hybrid p–i–n photodiode/field effect transistor‐preamplifier combination.

Experimental comparison of a germanium avalanche photodiode and InGaAs PINFET receiver for longer wavelength optical communication systems

Abstract: The receiver sensitivity of an InGaAs PIN photodiode-GaAs MESFET hybrid optical receiver is compared experimentally with that of a germanium avalanche photodiode from 34 to 565 Mbit/s and over the temperature range 20 to 60°C.

High-speed-response InGaAs/InP heterostructure avalanche photodiode with InGaAsP buffer layers

Abstract: The optical response time of an InGaAs/InP heterostructure avalanche photodiode (HAPD) with InGaAsP buffer layers is reported. It is shown that the buffer layers play an important role in reduction of the pile-up effect and are considered to be effective in achieving high-speed InGaAs/InP HAPDs.

The channeling avalanche photodiode: A novel ultra-low-noise interdigitated p-n junction detector

Abstract: A novel avalanche photodiode (APD) concept, the channeling APD, is proposed. Using a new interdigitated p-n junction structure, electrons and holes are spatially separated and impact ionize in layers of different band gap. Thus the effective ionization-rates ratio can be made extremely high (κ = α/β > 100), while maintaining a high gain, by a proper choice of the band gap difference. In the limit of large κ, this device mimics a channeltron photomultiplier. This structure can be fabricated using most III-V lattice matched heterojunctions, including long-wavelength materials for fiber-optical communications ( 1.3 \leq \lambda µm). The design of three channeling APD's using Al 0.45 Ga 0.55 As/ GaAs, InP/In 0.53 Ga 0.47 As, and AlAs 0.08 Sb 0.92 /GaSb heterojunctions is discussed in detail. Other important features of this structure are the unique capacitance-voltage characteristic, which may be important in varactor diode applications, and the interdigitized geometry which allows the depletion of large volumes of semiconductor materials doped to levels as high as 1017/cm3. This novel semiconductor device may find interesting applications also for FET's and integrated p-i-n-FET receivers and may be used for studies of high-field transport phenomena (e.g., drift velocities) over a wide range of electric fields.

Gain and bandwidth of fast near-infrared photodetectors: A comparison of diodes, phototransistors, and photoconductive devices

Abstract: Different materials and different types of detectors are used for optical data communication in the wavelength range of \lambda \sim 0.8 µm \lambda \sim 1.7 µm. In this paper the behavior of p-n diodes, Mn and Mp Schottky diodes is evaluated as well as that of bipolar transistors, n-p-n and p-n-p, and of photoconductive detectors using n-type or p-type material. The different behavior of lateral and coaxial versions is shown taking into account contact and surface recombination. The gain, the bandwidth, the gain bandwidth product, and the rise time of all these types of fast detectors are given in terms of material and technological data, including the discussion of the different rise and fall times of some detector versions. Finally, a theoretical comparison is made between the detectors showing their different behavior and ultimate performance limit. For practical GaAs planar devices as a photoconductive detector, a p-n diode, a heterojunction n-p-n and a lateral n-p-n transistor, a Mn Schottky diode, and a totally depleted MnM structure (symmetrical Mott barrier) experimental data are given. They verify the theoretical prediction that with all types of detectors rise times of <100 ps can be achieved.

Spectrophotometry and Spectrofluorometry with the Self-Scanned Photodiode Array:

Abstract: A state-of-the-art self-scanned photodiode array, utilized as a spectrometric multichannel detector, was studied for its applicability to molecular absorption and molecular fluorescence spectrometry. Molecular absorption spectrophotometry requires detectors with high UV to near IR response, high dynamic range, linear response, low noise, and temporal as well as thermal stability. Molecular fluorescence spectrometry requires, in addition, sensitivity to low-light level signals. These requirements were satisfied by the systems under study. Other parameters that govern the overall performance of diode array-based spectrophotometers and spectrofluorometers include: photometric range, stray energy radiation and its effect on photometric accuracy, photometric precision, spectral resolution sensitivity, and signal-to-noise considerations. Various readout methods for the array detectors were examined including: real time, in-memory signal integration, on-target signal integration, variable integration time (VIT), diode grouping, and diode fast access (a pseudorandom access readout). Performance demonstrations of these multichannel spectrometers were made with a few typical chemical systems. The spectrophotometric performance of the diode array system was excellent, practically equal to that of conventional single-channel systems. Exceptions were higher amenability to the adverse effects of stray radiation energy and a dependency of the geometric (wavelength) accuracy on spatial fluctuations (wander) in the light source. Potential long-term UV degradation of diode arrays may present an inherent problem, but was not discussed here because data accumulated up-to-date was considered inconsequential. As a spectrofluorometer multichannel detector, the diode array showed an "unexpected" signal-to-noise (detectability) performance, closely matching that of conventional high gain detectors. However, this performance was achieved only if sufficiently long signal integration times (20 to 160 s) were feasible. Overall performance of the diode array has demonstrated that theoretical multiplex advantages are achievable, resulting in either a considerable improvement in signal-to-noise or a corresponding shortening in observation time.

Monolithic integrated microgratings and photodiodes for wavelength demultiplexing

Abstract: The monolithic integration of micrograting filters and a photodetector array on a silicon substrate for optical wavelength demultiplexing is demonstrated. The demultiplexer is constructed with a series of micrograting filters fabricated by the electron beam direct writing technique in a chalcogenide (amorphous As2S3) film waveguide on a thermally oxidized silicon substrate and a Schottky barrier photodiode array fabricated on the Si surface.The device has the advantages of a high degree of design flexibility, high efficiency, low crosstalk, and very small dimensions. The design considerations and the fabrication process are described and the experimental results are discussed on the demultiplexing characteristics.

Solid-state image pickup device

Abstract: PURPOSE:To perform high speed operation, by using a junction type FET switch controlled with an address signal applied between the gate and the drain, and reading a current of a photo diode or a photo transistor CONSTITUTION:The unit consists of a photo diode consisting of a substrate 8 and a semiconductor layer 9, a junction type FET switch taking semiconductor layers 9 and 10 as the source and the drain and taking the substrate 8 as the gate, a source 11 driving the switch, an AND logical switch for X-Y address comprising a drain 12, and gates 13 and 8, and the unit switches picture elements A positive voltage is applied to the substrate 8 from a power supply 16 and a photoelectric charge is stored to the junction between the semiconductor layer 9 and the substrate 7 A voltage between the gate 8 and the drain 10 conducts between the gate 8 and the drain 10, to reset the charge of the photo diode and a reset current flowing at this time is read to form a photoelectric conversion signal

Sensitivity of avalanche photodetector receivers for long-wavelength optical communications

Abstract: We consider, in detail, the potential improvement in receiver sensitivity that can be realized using an avalanche photodiode (APD) rather than the conventional p-i-n diode in long-wavelength optical communications systems. Numerical computations are used to determine optimum gains and receiver sensitivities for several values of ionization coefficient ratios and dark currents. Sensitivities are considered for transmission bit rates of 45 Mb/s, 90 Mb/s, and 274 Mb/s — values characteristic of present long-wavelength systems. We find that general relationships and scaling laws between receiver sensitivity and the other critical parameters can be formulated if the sensitivity is calculated in units relative to the quantum limit. An important result is that the improvement in APD sensitivity depends strongly on dark current, but only weakly on the ionization coefficient ratio. Our calculations are compared with recent results obtained for In0.53Ga0.47As/InP APDs sensitive in the λ = 0.95 μm to 1.6 μm wavelength region. We also include a brief discussion comparing APD sensitivities with those obtained using phototransistors and majority carrier devices.

Bootstrap-transimpedance preamplifier for a fiber optic receiver

Abstract: A new preamplifier for use in fiber-optic receiver applications, or other applications in which a signal detector such as a photodiode is used that exhibits a large input capacitance to the receiver circuitry. The preamplifier combines transimpedance features to generate a voltage output from a current input signal generated by photodiodes used in such applications, and bootstrap features in which the capacitance of the photodiode is bootstrapped to reduce its effect on the receiver.

Bidirectional fiber optic transmission systems and photodiodes for use in such systems

Abstract: A single-wavelength, bidirectional fiber optic transmission system is described in which at each terminal the output radiation of a light source (LED or semiconductor laser) is coupled through a small diameter hole in the active area of a photodiode into the core of a larger diameter transmission fiber. On the other hand, radiation propagating through the fiber in the opposite direction exits from the fiber with a large NA so that most of it is incident on the active area of the photodiode and little is lost through the hole. Also described are a number of photodiode configurations for use in such a system, as well as dual photodiodes to perform both signal detection and output monitoring functions.

Picosecond optical electronic sampling: Characterization of high-speed photodetectors

Abstract: A photoconducting sampling gate which is triggered by a picosecond optical pulse and has an aperture of approximately 12 ps has been used to measure accurately the response of a high‐speed, solid‐state photodiode. The sample gate, which is made from a radiation‐damaged semiconductor, is demonstrated to have better speed, lower noise level, negligible jitter, and fewer reflections than conventional sampling oscilloscopes. In addition, it can be used over a wide temperature range by direct mounting in a variable temperature cryostat.

A photodiode array detection system: Design concept and implementation

Abstract: Use of a linear photodiode array as the elemental detector for an HPLC UV/Visible detector can provide both quantitative and semi-qualitative information for the analytical chemist. This paper discusses the primary needs of the analyst, the goals to be achieved in hardware and software, and possible applications for such a detection system.

AlGaAs/GaAs microcleaved facet (MCF) laser monolithically integrated with photodiode

Abstract: A new AlGaAs/GaAs double-heterostructure laser with microcleaved facets, restricted just at stripe contact edges, has been developed. This laser and a junction photodiode have been monolithically integrated in a single GaAs substrate. Low-threshold current lasing and high-fidelity monitoring characteristics have been demonstrated.

Tunneling in the reverse dark current of GaAlAsSb avalanche photodiodes

Abstract: The reverse dark current of Ga0.8Al0.2AsySb1−y avalanche photodiodes was measured over a wide temperature range. The dark current at high voltages is dominated by a tunneling component which has been identified as defect tunneling because the tunneling energy is considerably less than the band‐gap energy. This identification is supported by the observation of a second tunneling component which becomes dominant at high electric fields.

Method and apparatus for adjusting a facsimile document scanner

Abstract: A facsimile document scanner 10 is illustrated which includes an optical system 23 having a folded optical path 40 and an adjustable lens system 42. A test pattern 60 in the form of a plurality of alternate light and dark stripes 64, 66 is focused upon a linear photodiode array 50 mounted in an integratd circuit pack 51. The number of light and dark stripes 64, 66 is equal to the number of photodiodes in the linear photodiode array 50 across the document width. For adjustment purposes, an oscilloscope 70 is connected to a serial output from the integrated circuit pack 50 and the position of the lens system along the optical path 42 is adjusted and a corresponding adjustment is made to the pointer of the lens holder 45 within the lens housing 43 to obtain the desired image size and focus. The position of the diode array 50 is adjusted with respect to the focused image 72, 74 to obtain the maximum display amplitude.

Long-wavelength (1.3- to 1.6-&#181;m) detectors for fiber-optical communications

Abstract: A review of the current status of long-wavelength InGaAsP and AlGaAsSb quaternary alloy photodetectors for fiber-optical communications is presented. The material properties important for this application are discussed and compared for each alloy system. High-purity material necessary for low-capacitance p-n junction detectors can be routinely prepared in the InGaAsP alloy system, and techniques have been developed for the growth of compensated low-carrier-concentration AlGaAsSb alloys to satisfy this requirement. The dark current of photodiodes in both quaternary alloy systems is often limited by tunneling, and high-purity material can also be used to reduce this component of the dark current. There is some indication that tunneling current may be defect-assisted rather than band-to-band. Device structures designed to reduce the electric field in the low band-gap materials and thus reduce the tunneling dark current are also reviewed. The special enhancement of the ionization-coefficient ratio β/α in AlGaSb devices is described, and recent results of measurements of α and β in

A sensitive and compact magnetometer using Faraday effect in YIG waveguide

Abstract: A new type of sensitive magnetometer with a very small probe is described. It is based on a novel hybrid configuration utilizing the Faraday effect in a ferrimagnetic optical waveguide. A linear polarized light generated by a semiconductor laser operating at 1.3 μm is coupled into a multimode magnetic plane waveguide made of a gadolinium gallium substituted YIG epi‐layer. The YIG film is of ‘‘easy in plane magnetization’’ type with a low saturation magnetic field. The Faraday rotation is detected with an infrared photodiode by measuring orthogonal polarization component. A polarization modulation technique at a frequency of 100 kHz is used to provide a high degree of noise rejection. The unknown magnetic field projection on the light propagation direction is measured by a zero magnetic field method based on the cancellation of the output signal at the modulating fundamental frequency. Characteristics of this magnetometer are presented. A sensitivity better than 10−7 Oe/Hz1/2 has been obtained at a frequen...