Frequency dependence of admittance of distributed surface states in MOS structures

A new interpretation for frequency response of capacitance and conductance due to the surface states of an MOS structure has been obtained. Contrary to the usual assumption that such measurements reveal surface states around the Fermi energy E_fn it has been shown that frequency response of capacitive reactance peaks around an energy E_m=E_fn+(kT/2) ln (1+ omega ² tau _m²) whereas the response function for conductance is constant between energies E_fn and E_m.