PHOTON-STIMULATED TUNNELING OF ELECTRONS IN SIO2 - EVIDENCE FOR A DEFECT-ASSISTED PROCESS

Photon-stimulated tunnelling (PST) of electrons at Si-SiO2 and SiC-SiO 2 interfaces is shown to be insensitive to the density and energy dist ribution of electrons in the semiconductors. Instead, the observed rel ation of PST to the type of the oxide layer indicates a defect level i n the oxide as the initial state of electrons contributing to PST. The defect's energy level was found to be positioned 2.8 eV below the con duction band of SiO2, the defect density increasing with silicon enric hment of the SiO2. The observed correlation between PST yield and dark conductance of the oxide suggests the isolated defect states to be in volved in the high-field electron transport of SiO2 layers.