A Single-Electron Transistor Produced by Nanoscale Oxidation of InAs

Atomic force microscope (AFM) oxidation was applied for the direct oxidation of a thin InAs layer in order to fabricate a single-electron transistor (SET) from an InAs/AlGaSb heterostructure. By employing the oxidized InAs as an insulator to form an in-plane-gate structure, SET structures were fabricated. For the improvement of the electrical properties of the InAs oxide as an insulator, a thinner InAs channel layer (10 nm) was introduced. This layer enables the AFM oxidation process at relatively low tip voltages with reduced tip wear. An improved breakdown voltage of as high as 1 V with a negligible leakage current of less than 1 nA was obtained. By using the 10-nm-thick InAs channel layer, SETs with a one- or two-isolated island structure were fabricated. The device characteristics measured at 4.2 K show SET characteristics confirming the successful formation of the gate insulator. While the SET with one island showed reproducible Coulomb oscillations, the other showed unstable oscillatory behavior due to the sensitivity of the structure to background charges. The improved SET characteristics evidenced by the clear Coulomb diamond structure indicate that the introduction of the thinner InAs channel layer is critical.