Alkali-metal-induced Fermi level and two dimensional electrons at   cleaved InAs(110) surfaces
  Low-temperature Hall measurements have been performed on two-dimensional electron gases (2DEGs) induced by deposition of Cs or Na on in situ cleaved surfaces of p-type InAs. The surface donor level, at which the Fermi energy of the 2DEG is pinned, is calculated from the observed saturation surface electron density using a surface potential determined self-consistently. The results are compared to those of previous photoelectron spectroscopy measurements. 
Masaaki Minowa, Ryuichi Masutomi, Toshimitsu Mochizuki, and Tohru   Okamoto