PERSISTENT PHOTOCONDUCTIVITY IN UNIFORMLY AND SELECTIVELY SILICON DOPED ALAS GAAS SHORT-PERIOD SUPERLATTICES

Hall and photo-Hall measurements have been carried out between 4 K et 400 K on MBE deposited AlAs / GaAs superlattices (SPS) with short period (25 angstrom < P < 50 angstrom) SPSs were uniformly or selectively doped with silicon. Galvanomagnetic measurements show that SPSs exhibited an electrical behaviour similar to that of Al(x)Ga1-xAs:Si alloy (0.32 < x < 0.35). The Hall mobility was increased under illumination and persistent photoconductivity (PPC) was observed at low temperature (DX center). Thermal annealing of PPC was performed by increasing the measurement temperature. Two plateaus are observed in the n(H)(T) curves in uniformly doped SPSs whereas only one plateau was present in selectively doped SPSs. These experimental results are interpreted in terms of the multibarrier model of the DX center recently proposed in Al(x)Ga1-xAs:Si.