Influence of device geometry on SOI single-hole transistor characteristics

Abstract

SOI single-hole transistors have been fabricated by intentionally converting a quantum wire to an island connected to source and drain by two narrow constrictions. Two devices with different constriction lengths were investigated. It is found that slight differences in constriction lengths can lead to dramatic differences in device characteristics. For the device with short constrictions, periodic Coulomb oscillations are obtained and persist at temperatures in excess of 100 K. The physical origin of the tunnel barriers of the device has been analyzed experimentally and investigated theoretically based on the self-consistent numerical results of the Schrödinger and Poisson equations. The result indicates that lower ground-state energy for holes in the narrow constrictions serves as a potential barrier responsible for the periodic Coulomb oscillations. For the device with longer constrictions, aperiodic drain current oscillations are observed. The analysis of the experimental results shows that the quantum wire connecting source and drain is converted into at least three islands, probably due to the pattern-dependent oxidation effect. Consequently, the charging energy combined with the quantum confinement energy for the smallest island gives rise to aperiodic drain current oscillations.