Transport characteristics of AlGaAs/GaAs wires fabricated by focused Ga-ion-beam implantation

Electron transport was studied in AlGaAs/GaAs wires fabricated using focused Ga-ion-beam implantation. Single-wire samples 0.2-10 μm wide and 20 μm long were prepared with various ion doses ranging 2×10 ¹¹-4×10¹² cm^-2; multiple-wire samples 0.1-0.3 μm wide and 10 μm long were prepared with an ion dose of 2×10¹¹ cm^-2. Electron mobility is reduced in the narrow wires because of the implantation-induced damage, and this mobility degradation is diminished by reducing the ion dose. These behaviors are consistently explained in terms of a diffusive scattering effect inside the channel and at the sidewall of the channel. Mobility in wires with the 2×10¹¹ cm^-2 ions is predominantly determined by the sidewall specularity. A 0.2-μm-wide wire with this ion dose exhibits a mobility of 2×10⁵ cm²/(V s) and a specularity above 0.8. These values exceed those previously reported for wires fabricated using ion implantation and probably arise from the annealing employed in the present work. Conductance steps are observed with a single 0.2-μm-wide wire, and enhanced transconductance steps occur in multiple-wire samples. These behaviors are related to mobility modulation that occurs when one-dimensional subbands cross the Fermi level.