[en] This patent describes a method of fabricating a buried heterojunction laser diode. It comprises providing a heterostructure including a single quantum well or multi-quantum well active layer vertically confined between a p-type cladding layer and an n-type cladding layer; and impurity disordering the heterostructure to delineate an active laser stripe, the step of impurity disordering the heterostructure including the steps of implanting a first chemical species into the heterostructure to create a first impurity disordered region within at least a portion of the active layer and one of the cladding layers; implanting a second chemical species into the heterostructure to create a second impurity disordered region within at least a portion of the active layer and the other one of the cladding layers; and activating the first and the second chemical species

[en] An optical technique for high-power radio-frequency (RF) signal generation is described. The technique uses a unique photodetector based on a traveling-wave design driven by an appropriately modulated light source. The traveling-wave photodetector (TWPD) exhibits simultaneously a theoretical quantum efficiency approaching 100 % and a very large electrical bandwidth. Additionally, it is capable of dissipating the high-power levels required for the RF generation technique. The modulated light source is formed by either the beating together of two lasers or by the direct modulation of a light source. A system example is given which predicts RF power levels of 100's of mW's at millimeter wave frequencies with a theoretical ''wall-plug'' efficiency approaching 34%

[en] Solid-state devices formed from compound semiconductor materials like GaAs, GaP, SiC, and (Al, Ga)As have long been viewed as candidates for use in electronic circuits functioning at temperatures greater than 300⁰C. To address the specific needs of power semiconductor devices operating simultaneously at high currents, voltages, and high temperatures, heterojunction devices formed from combinations of GaAs and (Al,Ga)As have recently been proposed. These novel heterojunction structures display reduced resistive and voltage parasitics when compared to wide-bandgap GaP or SiC homojunction diodes without seriously compromising control of thermally generated leakage currents. In this study a prototype, low-power, (Al, Ga)As/GaAs, heterojunction bipolar transistor (HBT) is described which has demonstrated excellent electrical characteristics in the 300 to 400⁰C temperature range. At 350⁰C, the HBT has a common-emitter current gain of 14 (V/sub CE/ = 5V, I/sub C/ = 10 mA) and collector-base leakage of 6.4 x 10^-2 A/cm² (V/sub CB/ = 5 V). These studies and others imply that a heterojunction, (Al Ga)As/GaAs, power semiconductor electronics technology is feasible in the near future

[en] We have measured transient and steady-state reflected As₄ and desorbing As₂ fluxes during molecular beam homoepitaxy on the (001) surfaces of GaAs, AlAs, and InAs. In the absence of growth, the reflected As₄ flux decreases, and the desorbing As₂ flux increases, with increasing temperature. In the presence of growth, both fluxes decrease linearly, and then saturate, with increasing group III flux. The saturated reflected As₄ flux depends on temperature, and ranges from approximately 1/2 at temperatures commonly associated with high-quality epitaxy, to zero at lower temperatures; the saturated desorbing As₂ flux is zero, independent of temperature. The reflected As₄ (but not the desorbing As₂ ) flux also depends on surface reconstruction, resulting in unexpected transients as surfaces sequence through various reconstructions upon initiation of growth

[en] We have observed multiple optical Bloch waves in a semiconductor photonic lattice. This photonic lattice comprises epitaxial quarter-wave periodic layers surrounding a periodic quantum-well region. After growth, the layers are structured laterally into periodic square unit cells by reactive-ion-beam etching. When photoexcited, the lattice emits a complex angular distribution of photons that reflects its periodic structure. Scattered light is distributed according to the Laue conditions in analogy with x-ray diffraction from a bulk crystal. Optical Bloch waves photostimulated in the lattice are analogous to electron Bloch waves in an atomic lattice. These optical Bloch waves exhibit long-range translational symmetry and local symmetry due to the shape of the unit cell. Interestingly, the far-field pattern of stimulated emission gives a direct mapping of the allowed Bloch wave vectors in the Brillouin zone. The mapping exhibits a wave-vector gap at the Bragg condition and may be associated with a photonic energy gap. In addition to measuring the intensity distribution of these Bloch waves, we directly measure the phase of the wave by polarization shearing interferometry

[en] The nanofabrication of two-dimensional photonic lattice structures in GaAs/AlGaAs is reported. The nanofabrication procedure combines direct-write electron-beam lithography and reactive-ion-beam etching to achieve etched features as small as 50 nm. The lattice comprises a hexagonal array of air cylinders etched into a semiconductor surface with a refractive index contrast of 3.54. A range of air volume fractions from 14% to 84% was investigated. The lithographic, masking, and etching processes necessary to fabricate the lattice are described along with practical limitations to achieving a lattice of arbitrary air volume fraction. Initial results from optical characterization of the lattice are also presented

[en] We have experimentally studied two-dimensional photonic lattices, honeycomb nanostructures, fabricated by electron beam lithography with (Al,Ga)As materials. Surface normal optical properties were investigated by measuring reflectance to determine the effective index of refraction and lattice stability against degradation. Also, continuous wave and time-resolved luminescence spectroscopy was used to assess electron-hole recombination. Finally, light scattering was employed to study photon coupling and propagation through the lattice. These measurements show that the structures are stable, that nonradiative surface recombination is present, and that resonant coupling of light into/out of the lattice occurs at selected wavelengths satisfying a Bragg condition

[en] This paper reports the development of gallium arsenide optically-triggered thyristors that exhibit tolerance to high x-ray dose rates. These two-terminal epitaxial devices feature breakover voltages of 18 V to 38 V with no radiation. They trigger at less than 2 volts with only tenths of mW of laser light, but do not trigger at 2 x 10⁹ Rad(Si)/s with a bias level as much as 40 to 60 percent of the zero-radiation breakover voltage. When these devices are bombarded with neutrons, the reduced carrier lifetimes result in a decreased sensitivity to triggering by light and ionizing radiation

[en] We report the first all-semiconductor Fabry--Perot-cavity reflectance modulators operating at wavelengths of 1.32--1.33 μm. These devices were grown on a GaAs substrate using an intermediate, linearly graded InGaAs buffer layer terminating in an In_0.33Ga_0.67As layer. The Bragg reflector stacks of the Fabry--Perot structure are composed of InGaAs and InAlAs layers lattice matched to the buffer, and the active cavity region is an In_0.4Ga_0.6As/In_0.26Al_0.35Ga_0.39As strained-layer superlattice. The key to obtaining device-quality material was low temperature growth (∼400 degree C) of the entire structure. For a device with a 0.38-μm-thick active region and a 4 dB insertion loss, we obtained a contrast ratio of ∼3:1 at 4 V bias

[en] Gallium arsenide optically-triggered thyristors that exhibit tolerance to high x-ray dose rates have been fabricated. These two-terminal epitaxial devices feature breakover voltages of 18 V to 38 V with no radiation. They trigger at less than 2 volts with only tenths of mW of laser light, but do not trigger at 2 x 10⁹Rad(Si)/s with a bias level as much as 40 to 60 percent of the zero-radiation breakover voltage. When these devices are bombarded with neutrons, the reduced carrier lifetimes results in a decreased sensitivity to triggering by light and ionizing radiation