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Surface potential distributions on InAs thin films grown on (110) GaAs substrates were studied by Kelvin probe force microscopy. The topography showed that their surfaces were covered by many terraces. The surface Fermi levels (EFS) were evaluated from the potential images, and EFSnear the terrace edge was higher than that on the terrace top, while both of them were above the conduction band edge of bulk InAs. These results indicate that the electrons are more concentrated near the terrace edge. The film thickness dependence of EFSwas also studied, but the quantum confinement effects in the InAs thin films were not confirmed experimentally.

Hot electrons were generated in n-doped GaAs/AlAs multiple quantum wells by optical intersubband excitation and their energy distributions were studied at 10 K. By measuring photoluminescence (PL) spectra, the hot-electron temperature Telwas quantitatively evaluated, taking into account such effects as the degenerate distribution of electrons, impurity-induced level broadening, and the distribution of holes. It was found that, when the intensity Pof the excitation was 30 kW cm-2, i.e. a few percent of the onset intensity for absorption saturation, Telincreased from 10 K to 120 K while the lattice temperature remained unchanged. When Pwas between 10 W cm-2and 30 kW cm-2, the rise of Telwas well explained by the balance between the photon energy absorption and the energy loss due to the LO phonon emission inside the ground subband.