Search

Presents a study that performed temperature-dependent Hall-effect measurements on pure, n-type, vapor-phase epitaxial gallium arsenide, irradiated by 1-MeV electrons at room temperature. Use of deep-level transient spectroscopy for electron-irradiation investigations; Measurements of the energies with respect to the valence band; Implications of the study.

Presents a study on convenient determination of concentration and energy in deep-level transient spectroscopy (DLTS). Introduction to DLTS; Characteristics of a reverse-biased, n-type Schottky diode; Derivation of equations; Results.

Presents a study which performed deep-level transient spectroscopy on silicon-doped gallium arsenide layers grown by molecular-beam epitaxy. Analysis of the semiconductor sample; List of parameters for electron traps; Comparison between the traps and the Hall-effect center.

Investigates the annealing dynamics of molecular-beam epitaxial gallium arsenide grown at 200 °C. Details of Hall-effect measurements and analysis; Results of absorption analysis; Factor which allows an annealing model to be formulated.

Shows that a thin, undoped molecular beam epitaxial GaAs cap layer grown on top of an n-type conductive layer significantly reduces the free-electron depletion from the latter. Reason behind free-carrier depletion in an n-type active layer; Poission equation solutions for the depletion loss.

The hole mobility of Be-doped (∼ 2 × 10[SUP17] cm[SUP-3]) AI[SUBx]Ga[SUB1-x]As, for x=0-1, is analyzed both theoretically and experimentally. Ahoy scattering is very important, and in fact reduces the hole mobility from 150 to less than 90 cm[SUP2]/V s at x=0.5. The main parameter in the alloy scattering formulation, the alloy potential E[SUBal], is found to be about 0.5 eV for p-type Al[SUBx]Ga[SUB1-x]As. [ABSTRACT FROM AUTHOR]

Provides evidence that the charge-balance analysis of temperature-dependent carrier-concentration data cannot distinguish between the donor and acceptor behavior of a center which is emitting carriers to a conduction band. Factors that can cause confusion; Comparison of donor and acceptor fits; Function of secondary ion mass spectroscopy.

Discusses expressions for the depletion width and capacitance transient applicable to traps which may be deep and of high concentration. Use of deep level transient spectroscopy; Depletion-approximation solution to the Poisson equation; Difference between the free-carrier depletion with and the deep-donor depletion width; Overview of the forward-bias pulse of length.

Presents information on a study which determined the hall scattering factors for electrons and holes in molecular beam epitaxial gallium arsenide by comparing carrier concentrations measured by the Hall effect with those measured by the elecrochemical capacitance-voltage technique. Insight on the Hall effect for measuring electron and hole concentrations in semiconductors; Methodology of the study; Results and discussion.

Evaluates the uniformity in [EL2], dislocation density, resistivity, mobility and carrier concentration for semi-insulating gallium arsenide wafers grown by the vertical-gradient-freeze technique. Description of the wafers used in the study; Method used to measure EL2 patterns.

Proposes a technique for whole-wafer etch-pit density (EPD) mapping in gallium arsenide (GaAs). Derivation of the quantitative relationship between fractional transmission and EPD; Illustration of an automated absorption apparatus useful in EPD mapping; Property of the pits formed on an etched GaAs surface.

Bulk, liquid-encapsulated Czochralski GaAs may be reversibly changed from semiconducting (ρ∼1 Ω cm) to semi-insulating (ρ∼107 Ω cm) by slow or fast cooling, respectively, following a 5 h, 950 °C soak in an evacuated quartz ampoule. This effect has been studied by temperature-dependent Hall-effect, photoluminescence, infrared absorption, mass spectroscopy, and deep level transient spectroscopy measurements. Except for boron, the samples are very pure, with carbon and silicon concentrations less than 3×1014 cm-3. Donor and acceptor concentrations, on the other hand, are in the mid 1015 cm-3 range, which means that the compensation is primarily determined by native defects, not impurities. A tentative model includes a donor at EC-0.13 eV, attributed to VAs-AsGa, and an acceptor at EV+0.07 eV, attributed to VGa-GaAs. [ABSTRACT FROM AUTHOR]

In order to study the enhancement of the ir response of photocathodes, a model describing the effects of absorption and interference within a semiconductor photocathode supported by a reflecting metallic substrate is developed. It is shown that the addition of a dielectric spacer between the metallic substrate and the cathode emitter to give a combined optical thickness of quarter wavelength enhances the quantum efficiency of photocathodes over a wider spectral range, and extends their maximum response toward the ir. With the choice of dielectric spacer thickness established by an optimum photocathode thickness, a broad spectral response is obtained with reasonably thin dielectric and thin photocathode layers. The absorption coefficient very strongly determines the degree of enhancement which is observed to increase rapidly at the longer wavelengths.

The spectral response of photocathodes is severely degraded toward the ir portion of the optical spectrum. This paper compares the quantum efficiency of the S-11 and the S-20 photocathodes, based on an absorption diffusion model, with their quantum efficiency as reported by the ITT spectral response curves. This comparison (ratio) shows that the irdegradation is due primarily to the poor escape probability of a low energy photoelectron over the surface potential barrier rather than degradation in absorption. This ratio is used to estimate an escape probability that is plotted as a function of photon energy.

By an analysis of the photodetection process, the response of photodetectors to wide band, noncoherent light and guidelines for its improvement are determined. In this paper, the phenomenon of multiple reflections within the emitter of a reflecting-translucent and a reflecting-opaque photocathode is analyzed. Geometrical and optical configurations and solid state parameters are evaluated in terms of their effect on the photodetection process. The quantum yield, the percent of incident light absorbed, and the collection efficiency are determined as functions of the thickness of the emitting layer. These results are then employed to suggest areas of improvement in the use of state-of-the-art photocathodes.

In order to evaluate methods of enhancing the response of state-of-the-art photocathodes, such as the S-20, we have used a mathematical absorption-diffusion model to study the effects of skewed incidence of light on the quantum efficiency. The phenomenon of increased optical absorption due to multiple reflections of light within the emitting layer-glass substrate combination is treated as a function of the angle of incidence. When the quantum efficiency generated for skewed incidence is compared with the quantum yield generated for normal incidence, a gain of 3.5 is predicted. The gain is greatest for the smallest absorption coefficient-photocathode thickness product.