In-plane gate single-electron transistor in Ga[Al]As fabricated by scanning probe lithography

A single-electron transistor has been realized in a Ga[Al]As heterostructur e by oxidizing lines in the GaAs cap layer with an atomic force microscope. The oxide lines define the boundaries of the quantum dot, the in-plane gat e electrodes, and the contacts of the dot to source and drain. Both the num ber of electrons in the dot as well as its coupling to the leads can be tun ed with an additional, homogeneous top gate electrode. Pronounced Coulomb b lockade oscillations are observed as a function of voltages applied to diff erent gates. We find that, for positive top-gate voltages, the lithographic pattern is transferred with high accuracy to the electron gas. Furthermore , the dot shape does not change significantly when in-plane voltages are tu ned. (C) 1999 American Institute of Physics. [S0003-6951(99)05242-0].