Showing papers on "Diode published in 1981"

Second-harmonic detection with tunable diode lasers — Comparison of experiment and theory

Abstract: A series of experiments are carried out by current modulating a tunable diode laser, and slowly ramping the wavelength to scan weak absorption lines in gases at pressures ranging from 2 to 60 Torr. A lock-in amplifier detects the second harmonic (2f) of the modulation frequency, and the experimental 2f signals are compared with theory. Detailed measurements are made on Lorentzian, Voigt, and Gaussian line profiles, over a wide range of modulation amplitudes. Excellent agreement between experiment and calculation is obtained in all cases. This quantitative understanding enables one to derive true lineshapes and linewidths of very weak absorption lines from measurements of 2f lineshapes only. Results are applicable to trace gas detection using tunable diode lasers, and to other areas of spectroscopy and magnetic resonance where harmonic detection techniques are routinely employed to monitor weak signals.

Light emitting diodes with high external quantum efficiency

Abstract: A light emitting diode is disclosed that emits light in the blue portion of the visible spectrum with high external quantum efficiency. The diode comprises a single crystal silicon carbide substrate having a first conductivity type, a first epitaxial layer of silicon carbide on the substrate and having the same conductivity type as the substrate, and a second epitaxial layer of silicon carbide on the first epitaxial layer and having the opposite conductivity type from the first layer. The first and second epitaxial layers forming a p-n junction, and the diode includes ohmic contacts for applying a potential difference across the p-n junction. The second epitaxial layer has side walls and a top surface that forms the top surface of the diode, and the second epitaxial layer has a thickness sufficient to increase the solid angle at which light emitted by the junction will radiate externally from the side walls, but less than the thickness at which internal absorption in said second layer would substantially reduce the light emitted from said top surface of the diode.

Towards picosecond resolution with single-photon avalanche diodes

Abstract: Avalanche p–n photodiodes with uniform breakdown over the junction area are known to be capable of single‐photon detection. An experimental study has been performed on the temporal resolution of these single‐photon avalanche diodes (SPADs) in measurements of the shape of ultrashort light pulses. By using an active‐quenching circuit, pulsed operation of the device has been obtained in accurately controlled conditions, avoiding spurious effects met in previous passive‐quenching circuits. Laser pulses with durations down to 150 ps FWHM have been used; the results obtained show that the resolution is remarkably better than this value. Performances and limitations of SPADs are discussed; temporal resolutions of a few tens of picoseconds may be expected.

Phthalocyanine organic solar cells: Indium/x‐metal free phthalocyanine Schottky barriers

Abstract: A thin organic film of polycrystalline particles of x‐metal free phthalocyanine (x‐H2Pc) dispersed in a polymer binder, when sandwiched between tin oxide (NESA) and indium electrodes, is shown to exhibit a strong photovoltaic effect. The photovoltaic and rectification properties of In/x‐H2Pc/NESA sandwich cells are reported. From the photovoltaic action spectra, the active region responsible for electric power generation was found to be confined to the metal/semiconductor interface. A Schottky barrier width of 300 A was determined, which allows the capture of 30% of solar irradiance. An electron trap density of 3×1017/cm3 and a Schottky barrier built‐in potential of 0.63 V are estimated from C‐V measurements. At low voltage, the dark current in the forward direction varies exponentially with voltage: from this dependence values of 2×10−9 A/cm2 and 1.3–2.6 for the saturation current J0 and diode quality factor n are determined. At higher voltage, a super quadratic dependence of forward current on voltage i...

A study of Pd/Si MIS Schottky barrier diode hydrogen detector

Abstract: Pd/Si MIS Schottky diode hydrogen detectors have been fabricated with a response of 2-3 orders of magnitude change in current for 154 ppm of H 2 in N 2 . Detailed evaluation of dark I-V, C-V, illuminated I-V, and internal photoemission data unambiguously ascribes the strong hydrogen sensitivity of these diodes to hydrogen-induced change in the work function of Pd, rather than to any surface-state effects. The reaction rate of the device to different gas ambients has been studied with time response measurements. A long-term degradation mechanism has been identified and traced to the poisoning of Pd by environmental sulfur. The role of oxygen and atomic hydrogen in determining the Schottky barrier height also is discussed in some detail.

The intrinsic electrical equivalent circuit of a laser diode

Abstract: The basic electrical equivalent circuit of a laser diode is derived. The effects of spontaneous emission and self-pulsations are included. It is found that self-pulsations are represented by a negative resistance in the model. Application of this model suggests purely electronic methods of suppressing relaxation oscillations in laser diodes.

Stationary and transient thermal properties of semiconductor laser diodes

Abstract: Numerical analyses and experimental results on thermal behavior of AlGaAs laser diodes for CW and modulated operations are presented. Theoretical stationary and transient temperature rises are calculated using Fourier and Laplace transformations. Effects of inhomogeneous heat flow to a submount and heat radiation from the diode surface into the ambient atmosphere are taken into account in the calculation. Thermal resistances of laser arrays are also discussed. Experimental temperature behavior at the active layer is obtained from the wavelength shift measurement of an oscillation mode using a birefringent filter, which provides fast and precise measurement. Three components of temperature rise are observed in step and periodic responses. Numerical and experimental results are in good agreement.

A temperature model for the GaAs MESFET

Abstract: This paper describes a new two-dimensional method for study of GaAs Schottky-barrier MESFET's. A modified form of the conduction current is used in which transport properties are described in terms of electron temperature rather than electric field. Nonequilibrium velocity effects such as velocity overshoot are included. Results for the one-dimensional GaAs diode and the two-dimensional GaAs MESFET are presented and compared to other studies that utilize the Monte Carlo procedure. Larger values of current cut-off frequency are predicted for submicrometer gate length MESFET's than in previous two-dimensional simulations which utilize the steady-state transport properties.

Charge injection over triangular barriers in unipolar semiconductor structures

Abstract: A theory of unipolar current over triangular barriers in semiconductor structures is developed. Diodes based on such barriers have been recently fabricated by molecular beam epitaxy using either variable‐gap or modulation‐doped semiconductors. In these diodes the current is due to unipolar injection of electrons. Exact analytic expression for current‐voltage characteristics is obtained. Comparison is made with recent experimental data.

Temperature and energy dependences of capture cross sections at surface states in Si metal‐oxide‐semiconductor diodes measured by deep level transient spectroscopy

Abstract: A new deep level transient spectroscopy technique is presented to determine capture cross sections at metal‐oxide semiconductor (MOS) surface states. The technique enables us to determine energy and temperature dependences of capture cross sections separately. Applying this method, electron capture cross sections at surface states in Si MOS diodes were measured and found to have strong energy dependence and rather weak temperature dependence. It was also found that there was an effect to increase the emission rate, which may be attributed to barrier lowering at the Si‐SiO2 interface.

Modelocking of Semiconductor Laser Diodes

Abstract: The history of modelocking of the semiconductor laser is reviewed. The theory of modelocking as it relates to the semiconductor laser diode system is developed and discussed. Experiments on semiconductor lasers at MIT and the Bell Laboratories under both active and passive modelocking conditions are described.

Very-high-speed back-illuminated InGaAs/InP PIN punch-through photodiodes

Abstract: Long-wavelength back-illuminated PIN photodiodes capable of detecting optical signals at multigigabit modulation rates have been fabricated and tested in a stripline circuit. A transit-time-limited response time of about 30 ps has been realised in a 25 μm-diameter diode.

Thermal impedance of diode lasers: Comparison of experimental methods and a theoretical model

Abstract: The thermal impedances of double heterostructure, oxide isolated, stripe geometry diode lasers were measured and compared to a calculated value from a theoretical heat‐flow analysis The lasers had a stripe width of 8 μm and a cavity length of 250 μm, and were bonded with indium solder to a gold/nickel plated copper block The measurement techniques were based upon the variation with active region temperature of four different device parameters: the terminal voltage, the emitted optical power, the longitudinal‐mode spectrum, and the lasing threshold current As predicted by the theoretical analysis, the thermal impedance measurements based upon the various parameters yielded the same measured thermal impedance, indicating that each parameter responded to the same average active region temperature The range of values measured for different diodes was 33 to 79 °C/W, compared to the theoretically calculated value of 25 to 30 °C/W The wide range of measured values is attributed to irregular conditions assoc

Speckle Noise Reduction in Fiber Optic Analog Video Transmission Using Semiconductor Laser Diodes

Abstract: This paper investigates the effects of speckle noise on analog video transmission systems using semiconductor laser diodes. The system linearity degradation due to speckle noise is examined using different fiber types. Then this paper proposes a new modulation technique employing a superimposed pulse scheme to reduce speckle noise. It is experimentally confirmed that the proposed modulation method is effective in reducing speckle noise. Based on the above investigations, analog video transmission experiments are performed using single-mode fibers, step-index multimode fibers, and graded-index multimode fibers in the 0.8 and 1.3 μm wavelength regions. The results of the transmission tests have confirmed the feasibility of analog video transmission using semiconductor laser diodes.

Planar multimode detector arrays for infrared and millimeter-wave applications

Abstract: A new type of detector array is described. By means of a suitably designed metallic network, many detector elements (each individually small compared to wavelength) are assembled into an impedance-matched termination for radiation incident normally on the plane of the device. Residual reactance is tuned out by means of a movable backshort. An array of 400 bismuth-film microbolometers with a total area of 1 cm2has been tested at 215 GHz. A coupling efficiency of approximately 60 percent was observed. The detector has a D* of 4 \times 10^{8} cm . Hz1/2/W at room temperature with response time on the order of 2 \times 10^{-7} s. Similar arrays of Schottky and SIS diodes can probably be constructed.

Picosecond optical pulse generation at gigahertz rates by direct modulation of a semiconductor laser

Abstract: We report the generation of picosecond pulses by the direct modulation of a buried heterostructure GaAlAs diode laser. Pulse width of 28 ps is achieved at a repetition frequency of 2.5 GHz. Pulse width dependence on the experimental parameters is described.

Grain boundaries in p‐n junction diodes fabricated in laser‐recrystallized silicon thin films

Abstract: Grain boundaries intersecting metallurgical p‐n junctions have been evaluated in laser‐recrystallized silicon thin films. Lateral p‐n junction diodes were fabricated in islands of polycrystalline silicon which were defined on an amorphous substrate and cw laser recrystallized. The oxide‐passivated diodes display good current rectification. Correlated scanning electron microscopy (electron‐beam induced current and voltage contrast) and transmission electron microscopy reveal that the electrical junction strongly deviates from the linear boundary between the n and p regions defined by ion implantation. Spikes in the junction profile arise from enhanced dopant diffusion along grain boundaries.

Optical Pumping by Lasers in Atomic Frequency Standards

Abstract: Summary Single-mode, near-infrared diode lasers may improve the performance of atomic frequency standards. In the case of rubidium standards, the short-term stability may be improved by using laser diodes for optical pumping in place of conventional rf-excited lamps. In cesium beam standards, the lasers may replace both sets of state selection magnets, resulting in signal-to-noise, more reliable beam detection, easily reversed beam direction for cavity phase shift measurement, reduced Majorana transitions, and a smaller, more easily regulated C-field. The degree to which these improvements are realized depends upon the characteristics of available lasers. In this paper, we report measurements of laser intensity and frequency noise and their effects on clock performance. The light shift in a laser-pumped Rb clock is given, as well as the stability curve for that clock. Preliminary work on optical pumping in a cesium beam is also reported.

Measurement of Richardson constant of GaAs Schottky barriers

Abstract: The Richardson constants for near-ideal AuGaAs and AlGaAs Schottky diodes have been determined from an analysis of forward current-voltage characteristics. Measurement of capacitance-voltage characteristics at different temperatures shows that the barrier heights of the diodes have very similar temperature dependence for both Au and Al contacts. On taking into account the temperature dependence of the barrier height, the corrected value of the Richardson constant for AuGaAs diode is found to be very close to the predicted theoretical value. The corresponding value for AlGaAs diode is about a factor of five smaller which is explained on the basis of a thin interfacial layer between Al and GaAs.

Bulk and surface states analysis in a‐Si:H by Schottky and MIS tunnel diodes capacitance and conductance measurements

Abstract: An experimental and theoretical study of both the capacitance and the conductance of Schottky and MIS tunnel diodes made on undoped a‐SI:H, versus frequency, temperature, and voltage is presented in this paper. It is based on a general model using an equivalent electrical circuit of the devices, which permits an unambiguous distinction to be made between the contributions of bulk surface states, to determine their respective densities and to analyze their kinetic properties, It is shown that the bulk density of states (DOS) can be determined from capacitance and conductance measurements versus temperature and frequency on both Schottky and MIS devices, provided the modulation frequency is high enough to prevent any contribution from surface states. It is demonstrated that capacitance‐voltage characteristics of Schottky diodes cannot provide reliable information about either bulk or surface as the diffusion theory and not the thermionic theory is appropriate to describe the transport of electrons across th...

Antenna with P.I.N. diode switched tuning inductors

Abstract: A tuned radio antenna for a frequency agile communication system has a plurality of tuning inductors in series with a short-circuiting switch for each inductor, each switch being formed by a pair or a plurality of pairs of P.I.N. diodes, control means being provided for applying biasing potentials to the diodes to effect switching of the antenna tuning.

Method and apparatus for focusing a laser beam on an integrated circuit

Abstract: A laser beam (38) is focused on the surface of a semiconductor substrate (10) by translating an objective lens (70) along the path of the laser beam (38). The substrate (10) is fabricated to have a region (12) of an opposite conductivity type and to have a barrier layer (18) to the laser beam (38). An opening (16) is provided in the barrier layer (18) to permit the laser beam (38) to strike the substrate (10). A voltage source (24) and resistance (26) are connected in series between the substrate (10) and the region (12) to form a reverse biased diode junction. When the laser beam (38) strikes the substrate (10) charge carriers (42) are generated to produce a current through the resistor (26). The current flow through the circuit is measured by a control circuit (84) which drives a mechanism (72, 74, 76, 78, 80) to position the objective lens (70) such that the focus point of the laser beam (38) is positioned at the surface of the substrate (10). The maximum current flow through the PN junction is produced when the maximum intensity of laser energy is directed to the substrate (10). The primary application of the focusing apparatus disclosed herein is for burning out links to substitute redundant circuit elements for defective elements in an integrated circuit.

Depletion layer effects in the open-circuit- voltage-decay lifetime measurement

Abstract: There is a renewal of interest in open circuit voltage decay as a technique for determining the base region minority carrier lifetime in semiconductor diodes. Although the existing theory of open circuit voltage decay provides a substantial foundation for interpreting the experimental data, major features of the decay curves of real silicon diodes cannot be satisfactorily explained unless depletion layer effects are taken into account. Theoretical decay curves are calculated to show the effects of depletion layer capacitance and recombination current on the otherwise ideal open circuit voltage decay. From these and from experimental decay curves, it is shown that each of these depletion layer effects is significant only below a threshold junction voltage that depends upon material parameters of the device.

High-power subnanosecond switch

Abstract: A triggering mechanism, unconnected with carrier transfer effects at long distances, for power commutation of 105–106 W in the subnanosecond range, is believed to have been found from the study of the avalanche breakdown process. The switching time does not increase when the diodes are connected in series.

Chapter 7 Metal-Insulator-Semiconductor Infrared Detectors

Abstract: Publisher Summary This chapter reviews the current status of mercury cadmium telluride, (HgCd)Te, metal–insulator–semiconductor (MIS) technology with particular regard to its application in the field of detection of infrared radiation. The performance of the MIS thermal equilibrium mode detector is seen to be equivalent to that of an open-circuit photodiode. Background limited operation (BLIP) can be achieved although with smaller peak responsivity values than for a photodiode operated at V = 0 in which the MIS diode impedance is determined by the background photon flux and not by thermally generated currents. The detector signal under these BLIP conditions is, however, independent of device quantum efficiency. The dominant redeeming feature of the MIS photodiode as compared to the metallurgically formed photodiode is the relative ease of device fabrication, the absence of processing extremes such as ion implantation, high-temperature annealing, and high-temperature diffusion to form the photosensitive junction, and the degree of control over surface leakage. In effect, the quality of the MIS photodiode is determined almost completely by the properties of the substrate material.

Thermopile type detector with temperature sensor for cold junction

Abstract: A thermopile type detector which is constituted by an electrically insulating film, a thermopile supported on the film, a semiconductor substrate supporting the film, and a temperature sensing element on the surface of the substrate on which the film is supported and in the neighborhood of a cold junction of the thermopile. The temperature on the substrate immediately adjacent a cold junction of the thermopile can be measured for use in compensating the output of the thermopile for the changes in temperature of the cold junction. The temperature sensing element can be a semiconductor material such as a diode or a transistor forming a semiconductor with the substrate.

Scanning laser spectrometer

Abstract: A scanning spectrometer incorporating a scanning diode laser powered with a controllable injection current. The injection current control may be set at predetermined discrete levels. These levels may be varied in accordance with signals derived from a servo loop, and may have superimposed upon them a cyclically varying substantially constant amplitude current. The laser output is directed via a beam splitter to both sample and reference cells. The material in the reference cell is so selected as to provide absorption features at each of the desired frequencies. The cyclically varying current is provided with an amplitude sufficient to cause a frequency amplitude at least as great as the maximum breadth of each of these spectral features of interest. The preselected bias currents are selected so as to provide lasing action of the diode at or near each of the selected frequencies. A phase-locked amplifier tuned to the frequency of the cyclically varying current senses the position of the scanned laser output relative to that of the associated absorption feature and provides an error signal to adjust the bias current so as to center the cyclically scanned laser frequency on the selected absorption feature.

Laser diode switch

Abstract: Optical switches using laser diodes are proposed. Basic switching operation using an AlGaAs CSP laser is demonstrated for the first time. Isolation is better than 71 dB, signal bandwidth is broader than 1.5 GHz, and switching time is shorter than a few nanoseconds.