Thermal emission of holes from defects in uniaxially stressed p-type silicon.

Abstract

Iron-acceptor pair defects in silicon are insensitive to stress. These defects therefore provide convenient reference points from which to measure the effects of uniaxial stress on the valence-band structure in silicon. Despite the strong mixing of light- and heavy-hole bands at low values of stress, we find that for thermal emission the stress-split valence band can be approximated as two independent bands that displace rigidly with increasing stress according to the shear deformation potentials. The spherical approximation for the effective masses is not consistent with these deformation potentials because the approximation incorrectly partitions the density of states between the two bands. We establish the correct partitioning of the density of states numerically, and find stress-dependent density of states that approximately conserve the center of gravity of the split valence bands. Uniaxial stress data on the Fe-Al defects in silicon are used to experimentally verify the numerical results. The analysis described in this paper can be easily generalized to determine the stress properties of hole traps in any p-type semiconductor.