New direct spectroscopic method for determination of the energy distribution of interface states

Energy distribution of interface states for Si-based MIS solar cell devices with an ultra-thin oxide layer of ~2.5 nm is obtained from measurements of X-ray photoelectron spectra under biases. The interface spectrum for the native oxide layer has one peaked-structure near the midgap with a density maximum of ~2×10¹³ cm^-2 eV^-1, and it is attributed to an isolated Si dangling bond. For the chemical oxide layer formed with HNO₃, the interface spectrum has two peaked-structure with much reduced density. The peak below (or above) the midgap is attributed to a Si dangling bond weakly interacting with a Si (or oxygen) atom in the oxide layer. In is shown that an increase in the ideality factor is caused by both the static and dynamic effects of the interface states