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Discusses a study that focused on minority-carrier recombination kinetics and transport in GaAs/Al[subx]Ga[sub1-x]As double heterostructures. Aspects of epitaxial growth techniques that may be superior to liquid-phase-epitaxy prepared heterostructures; Factors that affect free-carrier recombination kinetics; Advantages of the Haynes-Shockley transport measurement technique.

Examines the properties of high-purity Al[subx]Ga[sub1-x]As grown by the metal-organic vapor-phase-epitaxy (MOVPE) technique using methyl precursors. Information on the growth and characterization of high-purity MOVPE semiconductor; Electrical properties of the semiconductor; Optical properties of semiconductor.

We show that the radiative efficiencies and lifetimes of photoexcited carriers in epitaxial GaAs may both be enhanced by three to four orders of magnitude by the preparation of thin n+, doped layers at the surface and substrate interfaces. Samples were prepared by organometallic vapor phase epitaxy with n- region (∼1015 cm-3) thicknesses of 3–10 μm and n+ regions Si doped to concentrations of 5×1018 cm-3. Time-resolved luminescence in such structures (25–300 K), under both surface and bulk (near-band- edge) excitation conditions, reveals band-to-band-dominated recombination spectra, with carrier lifetimes ranging from a minimum of 150 ns at 50 K to 800 ns at room temperature. This is in sharp contrast to the subnanosecond lifetimes and poor raditive efficiencies typical in conventionally prepared, bulk or epitaxial GaAs, but is comparable to the best reported for high-purity LPE GaAs/AlxGa1-xAs double heterostructures. [ABSTRACT FROM AUTHOR]

The absolute determination of the Al concentration, x, in epitaxial layers of AlxGa1-xAs was carried out using a nuclear reaction technique. This technique utilizes the narrow resonances found in the 27Al( p,γ)Si28 reaction, together with Rutherford backscattering measurements, to obtain accurate values of the alloy composition. The AlxGa1-xAs band edge was measured on these samples through low-temperature photoluminescence (2 K) measurements. An improved value of the direct edge (Γ) on composition was determined to be EΓg =1.512 +1.455x(eV) within a ±0.3% limit. The direct-to-indirect transition was found to occur at an Al concentration of x[bar_over_tilde:_approx._equal_to]0.37±0.015, lower than previously reported for He temperatures. [ABSTRACT FROM AUTHOR]

Structural [nuclear magnetic and electron spin resonance (ESR), infrared spectroscopy], optical (absorption, photoacoustic, photoluminescence), and electrical data are presented for amorphous hydrogenated germanium (a-Ge:H) prepared by homogeneous chemical vapor deposition (HOMOCVD). Like HOMOCVD prepared amorphous hydrogenated silicon, these a-Ge:H materials exhibit very low ESR spin densities and systematically varying optical gaps and hydrogen contents. Nevertheless, the material displays no subband gap photoluminescence and minimal photoconductivity, suggesting that a spinless defect may ultimately limit the device application of all types of a-Ge:H and a-(Ge,Si):H films. [ABSTRACT FROM AUTHOR]