Diamagnetic susceptibility of amorphous III-V compound semiconductors

Abstract

We analyse, for the first time, the effect of bond angle disorder on the diamagnetic susceptibility ( chi ) of a model amorphous III-V compound semiconductor by using a linear combination of hybrids formalism. We introduce distortion in the bond angles and construct an orthonormal basis set for the disorder network to derive an expression for chi of amorphous semiconductors in terms of the bond-angle distortion parameter Delta . We obtain chi ( Delta )= chi c+ chi v( Delta )+ chi p( Delta ), where chi c is the core diamagnetic term, independent of Delta . chi v( Delta ) is the Langevin-like diamagnetic term due to valence electrons, which varies very slowly with increasing Delta . However, chi p( Delta ), which is the Van Vleck-like paramagnetic contribution, decreases with increasing Delta . For covalent semiconductors (Si, Ge) chi v(O) and chi p(O) ( Delta =0.0 corresponds to crystalline value) are individually large and nearly cancel each other. Therefore, reduction in chi p( Delta ) with increasing Delta drastically increases the total susceptibility chi ( Delta ), giving rise to large diamagnetic enhancement. However, for Ill-V compound semiconductors, the magnitude of chi v(O) is large compared to chi p(O). Therefore, the decrease in chi p( Delta ) hardly affects the total susceptibility, leading to a small diamagnetic enhancement in the amorphous phase.