Characteristics of surface states and charge neutrality level in Ge

The characteristics of surface states on Ge are investigated using metal/insulator/semiconductor structures and the conductance technique. Evidence of acceptor-like and donor-like surface states on the valence band side of the Ge bandgap is shown by trap time constant analysis. The dependency of trap time constants on trap energy separation from band edge, capture cross section, and temperature are studied through conductance measurements and simulations. The effect of surface states on the location of charge neutrality level at the Ge surface and the consequences such as surface conductivity and negative charge buildup at the interface are discussed. (C) 2009 American Institute of Physics. [doi:10.1063/1.3270529]