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Above room temperature electronic transport properties of SrxTiyO3-δ films with cation A/B = (La + Sr/Nb + Ti) ratios of 0.9 to 1.2 are compared to STO single crystals with combined Hall carrier densities of 3 × 1016 cm-3 ≤ nH ≤ 1022 cm-3. In contrast to Hall mobility which is single crystal-like (μH ≈ 6 cm2/Vs) only near A/B = 1, the Seebeck coefficient (S) is single crystal-like over a range of nonstoichiometry. For nH < 1020 cm-3, S is well described by nondegenerate band-like transport with a constant effective mass m*/mo ≈ 5-8. For nH > 1021 cm-3, S is metallic-like with m*/mo ∼ 8. No marked increase in m* with decreasing nH owing to a carrier filling dependence is observed. [ABSTRACT FROM AUTHOR]

Photocurrent (PC) spectroscopy under high electric fields perpendicular to the heterointerface has been utilized to characterize subband structures in GaAs/AlGaAs multiple quantum wells (MQW’s). The PC spectra from MQW’s under high electric fields show clear exciton peaks corresponding to forbidden transitions between electron and hole subbands. From PC spectra, we have precisely determined the splitting energies of the two lowest electron and four highest hole subbands in 55-, 82-, and 105-Å-thick wells. The experimental results indicate that the conduction-band offset is 60±3% of the band-gap discontinuity. Our data are also in excellent agreement with finite square well calculations using a heavy-hole effective mass of 0.34 and a light-hole effective mass of 0.12. [ABSTRACT FROM AUTHOR]

Raman scattering from Si-doped n-AlxGa1-xAs (x=0.25) grown by molecular beam epitaxy has been studied at room temperature. In addition to the optical phonon lines, three new Raman lines have been clearly observed in samples with high carrier concentrations (n>=1×1018 cm-3). These lines are identified as the coupled plasmon-longitudinal optical (LO) phonon modes because their frequencies and relative intensities to the LO phonon lines depend on the excitation wavelength. [ABSTRACT FROM AUTHOR]