HELIUM RADIO-FREQUENCY-PLASMA GAAS DEVICE ISOLATION - APPLICATION TO AN INPLANE GATED QUANTUM WIRE TRANSISTOR

Low-energy ion bombardment has been used for isolation to define an in-plane gated quantum wire transistor in a GaAs/AlAs heterostructure. The two-dimensional electron gas (2DEG) was 17 nm below the GaAs/vacuum interface, with a mobility at 1.2 K of 7.97 x 10(5) and 6.3 x 10(5) cm2 V-1 S-1 at a sheet carrier concentration of 6.45 x 10(11) and 5.98 x 10(11) cm-2 with and without illumination, respectively. Optimum gate isolation was achieved using a 6 min exposure to a helium radio-frequency (rf) plasma at 5.7 Pa (43 mTorr), with a dc bias of - 150 V. Electrical measurements show that the application of a suitable gate bias produces conductance changes in the device, with evidence for one-dimensional (1D) ballistic transport at 1.2 K.