Accumulation capacitance of narrow band gap metal-oxide-semiconductor capacitors

We have investigated the accumulation capacitance-voltage characteristics for capacitors with narrow band gap materials using modeling and experiments. The capacitance for InAs and In0.53Ga0.47As capacitors with a HfO2 oxide layer has been calculated using atomistic tight-binding, effective mass, and semiclassical nonparabolic models. The simulations show that band structure effects have a strong influence on the accumulation capacitance, and are essential for the description of narrow band gap capacitors. The calculated tight binding data compare well with measurements on n-type InAs HfO2 capacitors on (100) and (111)B substrates, highlighting the nonparabolicity as the main origin for the large accumulation capacitance.