Optoelectronic properties of metal-tunnel oxide-silicon junctions

A new switching phenomenon was discovered in a simple Metal-Tunnel Oxide-N Silicon (MTOS) capacitor. Tunneling of holes prevents the build up of an inversion layer at the surface on application of negative bias and the semiconductor goes into deep depletion in which the junction impedance is high. Additional supply of holes from generation by light can increase surface hole concentration. When there is sufficient carrier generation, the surface can become inverted. In the process, the semiconductor voltage decreases and the oxide voltage is increased. Tunneling of electrons is controlled by oxide voltage and can be changed by orders of magnitude when the surface goes from deep depletion to inversion. The process described so far is reversible. The semiconductor goes back into deep depletion if generation by light is removed.