Two-dimensional electrons at a cleaved semiconductor surface:   Observation of the quantum Hall effect
  Low-temperature in-plane magnetotransport measurements have been performed on adsorbate-induced electron systems formed at in-situ cleaved surfaces of p-type InAs. The Ag-coverage dependence of the surface electron density strongly supports a simple model based on a surface donor level lying above the conduction band minimum. The observations of the quantized Hall resistance and zero longitudinal resistivity demonstrate the perfect two-dimensionality of the surface electron system. We also observed the Rashba effect due to the strong asymmetry of the confining potential well. 
Yukihide Tsuji, Toshimitsu Mochizuki, Tohru Okamoto