Russell E. Hayes

Ultralong minority-carrier lifetime epitaxial GaAs by photon recycling

The minority‐carrier lifetime has been measured by time‐resolved photoluminescence in epitaxial films of GaAs grown by metalorganic chemical vapor deposition. The measured lifetimes in thicker devices are 4 to 6 times the theoretical or radiative lifetime. These long lifetimes are the result of photon recycling or self‐generation of the self‐absorbed radiation.

Growth and patterning of GaAs/Ge single crystal layers on Si substrates by molecular beam epitaxy

Single crystal GaAs layers have been grown on Si substrates with an intermediate Ge layer. Both the Ge and subsequent GaAs are grown in situ by molecular beam epitaxy (MBE). Cross‐sectional transmission electron microscopy studies show GaAs surface dislocation densities on the order of 107 cm−2. The quality of the GaAs is indicated by a mobility within 15% of that measured on GaAs/GaAs MBE structures doped at the same level. This material also exhibits a photoluminescence signal with a room‐temperature intensity about 50% of GaAs grown on GaAs, and with a similar half‐width. In this letter, electron diffraction, optical and electrical data are presented for n‐type GaAs/Ge/Si structures. In addition, a selective lift‐off technique is demonstrated, with possible applications in the development of monolithic GaAs/Si integrated circuits.

Interfacial properties of indium tin oxide/indium phosphide devices

Efficient indium tin oxide (ITO)/p‐InP solar cells have been fabricated by ion beam deposition. In this letter, a critical evaluation of the ITO/InP interface is presented using complementary capacitance‐voltage and ion microprobe measurements. We have found that deposition of ITO produces a semi‐insulating region at the InP surface. This high resistivity layer extends about 750 A into the bulk. We have evidence that this region is due to surface accumulation of compensating impurities.

Numerical modeling of energy balance equations in quantum well Al/sub x/Ga/sub 1-x/As/GaAs p-i-n photodiodes

The energy balance equations coupled with drift diffusion transport equations in heterojunction semiconductor devices are solved modeling hot electron effects in single quantum well p-i-n photodiodes. The transports across the heterojunction boundary and through quantum wells are modeled by thermionic emission theory. The simulation and experimental current-voltage characteristics of a single p-i-n GaAs/Al/sub x/Ga/sub 1-x/As quantum well agree over a wide range of current and voltage, The GaAs/Al/sub x/Ga/sub 1-x/As p-i-n structures with multi quantum wells are simulated and the dark current voltage characteristics, short circuit current, and open circuit voltage results are compared with the available experimental data, In agreement with the experimental data, simulated results show that by adding GaAs quantum wells to the conventional cell made of wider bandgap Al/sub x/Ga/sub 1-x/As, short circuit current is improved, but there is a loss of the voltage of the host cell, In the limit of radiative recombination, the maximum power point of an Al/sub 0.35/Ga/sub 0.65/As/GaAs p-i-n photodiode with 30-quantum-well periods is higher than the maximum power point of similar conventional bulk p-i-n cells made out of either host Al/sub 0.35/Ga/sub 0.65/As or bulk GaAs material.

Time‐of‐flight studies of minority‐carrier diffusion in AlxGa1−xAs homojunctions

A novel time‐of‐flight technique has been developed for simultaneously measuring minority‐carrier lifetime and diffusivity in homojunctions. A pulsed dye laser produces electron‐hole pairs near the front surface of the device. A delay occurs before the onset of photocurrent due to the diffusion transit time of minority carriers to the junction. An analysis of this effect by both a simplified analytical model and a computer simulation gives similar results for the current as a function of time. A fit of the theory to experimental data on Al0.25Ga0.75As n/p homojunctions produces minority‐carrier lifetime, diffusivity, and diffusion length.

Measurement of the velocity-field characteristic of indium phosphide by the microwave absorption technique

The electron velocity-field characteristic has been determined for a large number of samples of InP by the microwave absorption technique. The values obtained for the electric field at the peak of the velocity-field curve are corrected for relaxation effects by comparison with a computer simulation, and the resulting values lie in the range 7.2-9.8 kV/cm-1. The corrected negative dynamic mobility just beyond the peak velocity varied between 0.3 and 0.5 of the low-field mobility.

Surface compensation of p‐InP as observed by capacitance dispersion

Very strong capacitance‐voltage dispersive effects are observed in mercury/indium phosphide Schottky diodes. These effects are related to a partially compensated region at the surface for which the Debye length is relatively large. The small‐signal capacitance is indicative of a critical dielectric relaxation time exceeding the period of the ac probe. This effect may be used to characterize the majority‐carrier profile in lightly doped or low mobility semiconductors.

Design of cathode doping notches to achieve uniform fields in transferred-electron devices

A numerical method for designing notch doping profiles for transferred-electron devices is presented. The profile is calculated to be consistent with a given uniform field in the active region and carrier density at the end of the notch. An example of this method is done for InP using a computer model which includes relaxation effects. For this example it is found that the required notch doping is p type and the active region doping is slightly nonuniform due to relaxation effects.

Saturation power in GaAs amplifiers

The results of an experimental investigation of the saturation power level of GaAs amplifiers are reported. It is found that there is an optimum range of applied voltages and electron density-length products to achieve the maximum saturation power. The largest saturation effciency observed was 4 percent.

EFFECT OF MULTIPLE REFLECTION PROPAGATION ON PHOTON RECYCLING IN GAAS/ALGAAS DOUBLE HETEROSTRUCTURES

An analysis is presented to accurately calculate the effects of photon recycling on the minority‐carrier lifetime in the active region of GaAs/Al0.3Ga0.7As double heterostructures. It is shown that the minority‐carrier lifetime multiplication factor and resulting minority‐carrier lifetime are dominated by multiple reflection propagation for samples with thicknesses of approximately less than 1.0 μm. The calculated results are in good agreement with previously published experimental data on the variation of the minority‐carrier lifetime multiplication factor with active region thickness, indicating the usefulness of the analysis to accurately model the effects of photon recycling in transient photoluminescence measurement of thin devices. This may lead to accurate determination of the minority‐carrier lifetime, diffusion coefficient, and surface recombination velocities at the levels of interest for device applications.