J. M. Woodall

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The photoexcited carrier lifetimes in ex situ-annealed low temperature growth GaAs are measured with a femtosecond transient absorption experiment. The study encompassed two low temperature growth GaAs films with approximately 0.3% and 0.9% excess arsenic incorporated during growth. The observed lifetimes are found to be a function of the spacing of arsenic(More)
Double-heterostructure GaAs/GaAlAs light-emitting diodes ~LEDs! have been fabricated with the emitter regions beryllium doped to 2310 and 7310 cm. The 7310 cm doped emitters have an internal quantum efficiency of 10% and an optical modulation bandwidth of 1.7 GHz. The steady-state optical output power versus the input current shows an external efficiency of(More)
We report high-speed digital modulation of GaAs–AlGaAs light-emitting diodes. Open eye patterns and bit error rates less than 10 9 were obtained for data rates from 750 Mb/s to 1.7 Gb/s. These results are the first report, to our knowledge, of error-free digital modulation experiments for LEDs at bit rates above 1 Gb/s.
The experimental observations of metallurgical interactions between compound semiconductor substrates and metallic or oxide overlayers have stimulated a new model of Fermi level "pinning" at these interfaces. This model assumes the standard Schottky picture of interface band alignment, but that the interface phases involved are not the pure metal or oxide(More)
Characteristics of high-voltage dual-metal-trench (DMT) SiC Schottky pinch-rectifiers are reported for the first time. At a reverse bias of 300 V, the reverse leakage current of the SiC DMT device is 75 times less than that of a planar device while the forward bias characteristics remain comparable to those of a planar device. In this work, 4H-SiC(More)
Epitaxial layers of GaAs have been grown by metalorganic molecular beam epitaxy (MOMBE) with atomic carbon concentrations ranging from 4 X 10 17 to 3.5 X Ufo cm --I. The dependences of GaAs lattice parameter and hole concentration on atomic carbon concentration have been determined from x-ray diffraction, Hal! effect, and secondary-ion mass spectrometry(More)
Recently, GaN-based materials have been intensively studied for optoelectronic devices and hightemperature/high-power electronic devices, and visible light-emitting diodes,1 ultraviolet (UV) detectors,2 microwave-operation AlN/GaN field-effect transistors (MESFETs),3,4 and high-electron-mobility transistors (HEMTs)5 have been demonstrated. As device(More)
Using GaAs epilayers with arsenic precipitates (GaAs:As) as the photoconductive material in a broad-band optoelectronic terahertz beam system, we have generated and detected freely propagating, subpicosecond electromagnetic pulses. The receiver signal gave a measured integrated pulse width of 0.71 ps. Fast photoconductive rise times have been achieved which(More)
Practical design of high-voltage SiC Schottky rectifiers requires an understanding of the device physics that affect the key performance parameters. Forward characteristics of SiC Schottky rectifiers follow thermionic emission theory and are relatively well understood. However, the reverse characteristics are not well understood and have not been(More)