Diameter dependence of current–voltage characteristics of ultrasmall area AlSb–InAs resonant tunneling diodes with diameters down to 20 nm

We have studied the current–voltage characteristics I(V) of ultrasmall area AlSb–InAs resonant tunneling diodes (RTDs) with diameters down to 20 nm. Resonant tunneling peaks were observed for all the diodes at room temperature. The peak-to-valley ratio reduces with the decreasing diameter of the RTD. We found from the diameter dependence of the valley current that the reduction is due to a contribution of the thermally activated surface current to the valley current. For RTDs with diameters less than 100 nm, we observed fine structures around zero bias at 4 K. They can be attributed to tunneling through zero-dimensional states confined by a RTD sidewall.