A single-electron transistor produced by nanoscale oxidation of InAs

Atomic force microscope (AFM) oxidation was applied for the direct oxidatio n 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 fabri cated. For the improvement of the electrical properties of the InAs oxide a s an insulator, a thinner InAs channel layer (10 nm) was introduced. This l ayer enables the AFM oxidation process at relatively low tip voltages with reduced tip wear. An improved breakdown voltage of as high as 1V with a neg ligible 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 cha racteristics confirming the successful formation of the gate insulator. Whi le the SET with one island showed reproducible Coulomb oscillations, the ot her showed unstable oscillatory behavior due to the sensitivity of the stru cture to background charges. The improved SET characteristics evidenced by the clear Coulomb diamond structure indicate that the introduction of the t hinner InAs channel layer is critical.