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Research describing the photoreflectance at 300k of a chirped superlattice heterojunction bipolar transistor structure is presented. The inbuilt dc electric fields and associated doping levels are investigated.

Abstract: AZ80 cast magnesium alloy has been fabricated by a combination of ECAE (equal channel angular extrusion) and subsequent forging processing to investigate the effect of second forging processing on the evolution of microstructure, texture and tensile properties. The AZ80 alloy produced by this process exhibited the ultimate tensile strength (UTS) of 434MPa, yield strength (YS) of 347MPa, and elongation-to-failure of 6%. The observed high strength in this sample has been ascribed to the effect of grain refinement and the formation of sharp basal texture by the subsequent forging processing. The contribution of second-phase particles to the mechanical properties was also discussed in this paper. [Copyright &y& Elsevier]

Doping results from Ar[sup +] laser-assisted chemical beam epitaxy with triethylgallium, tris(dimethylamino) arsenic, and silicon tetrabromide precursors are reported. Enhancements in the n-type doping concentration are observed with laser irradiation in the substrate-temperature range 390-500 °C. With a 300 W/cm2 irradiation power density, a 70-fold increase in the carrier concentration is obtained at 390 °C substrate temperature. An expression for doping concentration is derived to assess the contribution of laser-induced thermal heating to the observed doping increase. Effects of photogenerated carriers on surface decomposition of metalorganic species are discussed. We postulate that the dramatic increase in carrier concentration at low growth temperatures is due to photolysis of silicon tetrabromide. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]