A Direct Tunneling Model of Charge Transfer at the Insulator-Semiconductor Interface in MIS Devices

Abstract : A general model of charge transfer at the insulator-semiconductor interface of metal-insulator-semiconductor (MIS) devices is developed. The model is based upon direct WKB tunneling of electrons from the semiconductor substrate into localized trap states within the forbidden gap of the insulator. Both an arbitrary distribution of the insulator states in energy as well as spatial variation in the trap densities in the interface region are treated. Advantage is taken of the strong spatial decay of the tunneling transition probability to obtain valid approximate solutions of the tunneling equations in a form directly amenable to numerical evaluation. The effects of internal electric fields in the insulator are included in a self-consistent manner. The results of several representative model calculations of post-irradiation annealing and field- injection characteristics of MIS capacitors are described.