We have grown thin films of a-Si:H and a-Ge:H by reactive magnetron sputtering and have studied their photoelectronic properties in surface cell structures. The dark and photocurrents do not obey the expected scaling laws with respect to changes in the sample thickness. This is explained in terms of a model which assumes depletion regions at both surfaces of the thin-film structure. We have analyzed the properties of such structures and have used the thickness dependence of the dark current and activation energy to estimate: (1) the defect concentrations near the Fermi level and (2) the amount of surface band bending. Defect densities so obtained are in agreement with those determined from space-charge limited currents (SCLC’s) and photodeflection spectroscopy (PDS).

Highly resistive hydrogenated amorphous-silicon film has been fabricated and examined as blocking-type photoconductive target of a vidicon-type image pickup tube. The results indicate that this novel silicon vidicon has many advantages over conventional ones.

The effect of stress on the current-induced degradation of current-voltage characteristics in AlGaAs/GaAs heterojunction bipolar transistors with Be-doped base layers is investigated. Transistors with different orientations of the emitter mesa and different thicknesses of the passivation film are bias tested at room temperature. The results are compared with the stress distributions along the emitter-base junction obtained from a two-dimensional calculation using the boundary element method. It is found that the degradation is caused by the diffusion of Be under high-current density operations and that the flux of Be diffusing from the base layer to the emitter layer is strongly related to the stress distributions around the periphery of the emitter-base junction.

Stable nonplanar surface formed on patterned GaAs (311)A substrate by molecular-beam epitaxy

The surface morphology of MBE-grown Be-doped GaAs was studied by RHEED, SEM and TEM. {411}A facets were found on the (100) surface for Be 6×1019 cm-3 doping at a growth temperature of 630°C. The surface roughness due to this faceting was suppressed by misorienting the GaAs substrate from (100) toward (111)A; a 19.5° misorientation, i.e., a (411)A substrate, was found to be effective in realizing a smooth surface, even for Be 1×1020 cm-3 doping.