Line Width of Inter-Subband Absorption in Inversion Layers: Scattering from Charged Ions

Abstract

The broadening of the inter-subband absorption is calculated in space-charge layers on a Si surface. Scatterers are assumed to be dominated by charged ions at the Si-SiO₂ interface. Among two different contributions to the broadening, the intra-subband process shows a drastic dependence on the strength of the depletion field, while dependence is smaller for the inter-subband process. The results explain recent experiments in accumulation layers on the Si (100) surface where extra Na⁺ ions are intentionally introduced at the interface.