Extension of Coulomb blockade region by quantum confinement in the ultrasmall silicon dot in a single-hole transistor at room temperature

First room-temperature (RT) observation of extended Coulomb blockade (CB) region due to quantum confinement in the ultrasmall silicon dot in a single-hole transistor (SHT) is described. We fabricate single-dot SHTs in the form of metal-oxide-semiconductor field-effect transistors with an extremely constricted channel. Both large CB oscillation with the peak-to-valley current ratio (PVCR) of 40.4 and clear negative differential conductance (NDC) with the PVCR of 11.8 (highest ever reported) are observed at RT in the fabricated device. The observed NDC is attributable to the resonant tunneling due to the large quantum level spacing in the ultrasmall dot whose size is estimated to be about 2 nm.