Carrier lifetime in MBE grown Si:Sb and Si:In layers measured by the transient grating method

Abstract

The carrier recombination dynamics in MBE grown silicon films, doped with Sb or In, are investigated by the transient grating method under strong pumping conditions with 35 ps laser pulses. The temporal decay of the induced gratings gives carrier lifetimes of the order 10-10-10-8 s for doping concentrations in the range 1017-1020 cm-3. A complementary theoretical evaluation of the lifetimes shows the importance of the different kinds of band-to-band Auger recombination increases with increasing doping concentration for Sb-doped Si. For In-doped (1017-1018 cm-3) Si and SRH recombination via in centres dominates. The measured lifetimes agree well with the theoretical values if it is assumed that, at the doping levels, internal stress increases the light absorption coefficient for lambda =0.53 mu m by a factor of up to 2 greater than the pure silicon value.