Quantum Hall effect at cleaved surfaces of InAs and InSb

The authors have performed low-temperature in-plane magnetotransport measurements on two-dimensional electron systems induced by adsorbates at in situ cleaved surfaces of p-type InAs and InSb. The Ag-coverage dependence of the surface electron density for InAs strongly supports a simple model based on a surface donor level lying above the conduction band minimum. For a cleaved surface of InSb, the quantum Hall effect was observed even at low magnetic fields around 2 T. The surface electron density and the electron mobility exhibit strong dependence on the adsorbate coverage and the annealing temperature in the range of 15–40 K. The annealing effect suggests that the surface morphology strongly affects the properties of the two-dimensional electron systems.