Effective masses of holes in non-(001) ultrathin Si layers

Abstract

We investigate the effects of crystallographic orientation on the quantization masses and the in-plane masses of valence subbands in ultrathin layers of Si within a six-band effective-mass theory. In order to provide physical insight on the difference in the quantum-confinement effects on these masses due to different crystal orientations, we adopt a square-well potential model with an infinite-barrier height. We show that in contrast to the case of (001)-oriented Si layers, the quantization mass of the heavy-hole subbands in (110)-oriented Si layers varies as a function of d/n, where d is the well width and n is the quantum number. In addition, we show that the sum of the reciprocal quantization masses of the heavy-hole, light-hole, and spin-orbit split-off subbands is constant, irrespective of d/n, in layers with an arbitrary orientation. The nonparabolicity of the in-plane dispersion of the first heavy-hole (h1) subband is shown to be reduced in (110)-oriented layers than in (001)-oriented ones of the ...