Measurement of hole leakage and impact ionization currents in bistable metal—tunnel-oxide—semiconductor junctions

The electron tunneling, oxide hole transport, and hot-electron impact ionization currents in bistable metal-tunnel-oxide-semiconductor (MTOS) junctions have been measured using a novel charge-coupled device charge packet insertion transient technique, and by steady-state hole injection. Good agreement was obtained between the two techniques. An electron-to-hole oxide current ratio in the range of 20-40 was observed for a 33-Å tunnel oxide. In addition, the impact ionization hole generation current was found to be 2-5 percent of the electron tunneling current. This excess hole generation appears to be balanced in the stable high current state by back diffusion from a super-inverted semiconductor surface. The impact ionization phenomenon results in a newly discovered voltage controlled n-type negative resistance when the MTOS junction is coupled to an adjacent p-n junction through the use of an intermediate control gate.