Motional binding in InAs with a realistic surface potential

The spatial dependence of the effective mass occurring in mass-mismatched quantum wells leads to a dependence of binding energy on transverse momentum. This ``motional binding'' has been observed in accumulation layers on narrow-band-gap materials, where the nonparabolicity provides the spatial dependence of the effective mass. To date, however, only a qualitative comparison has been made between experiment and theory. Here we use a model surface potential and a self-consistent potential to study motional binding in n-type InAs accumulation layers and find good agreement with experiment. The calculation shows that subbands are occupied over considerably larger ranges of surface-electron concentration than previously thought.