No abstract

Electric field effects on the thermal emission of traps in a diode have been studied. Calculations were performed and compared with experimental data on deep centers in GaAs. The results are consistent with a thermal equivalent of the optical Franz-Keldysh effect.

Porous silicon superlattices have been fabricated electrochemically. The current was monitored periodically during the electrolysis and samples were made with several periods. They have been investigated using reflectance measurements in the infrared and visible range. We demonstrate that porous silicon superlattices act like a multilayer dielectric device.

This study presents optical transmission measurements performed on free-standing homogeneous porous silicon (PS) films of different porosities and substrate doping levels. The absorption coefficient curves deduced from these measurements, taking into account the total quantity of matter in the PS film, exhibit significant blue shift (up to 500 meV). These shifts, well correlated with the crystallite size variations with porosity and substrate doping observed by electron microscopy and gas adsorption experiments, are attributed to quantum size effects in the silicon microcrystallites.

Experimental data are reported for the persistent photocapacitance quenching observed at 77 K in GaAs. This effect, which arises on the so-called oxygen (or EL2) center in gallium arsenide, is explained by the existence of two states of this center. The physical parameters of these stable and metastable states are given: optical cross section, annealing, and electrical deexcitation. Assuming a large lattice relaxation for the metastable one, a physical model is given with a possible microscopic origin. Other striking memory effects, and especially photoconductivity, are shown to be simply explained by our model.