Low-dimensional devices fabricated by molecular beam epitaxy regrowth over patterned δ-doped backgates

Abstract

Hydrogen radical decontamination of ex situ patterned GaAs wafers was successfully used to grow a two-dimensional electron gas (2DEG) only 160Å from the regrowth interface. Interface roughness scattering limits the mobility of this 2DEG to 330 000cm2/Vs. An initial growth incorporating a delta-doping layer is etched to expose a {411} facet intersecting this back gate and then a 2DEG is regrown over the patterned wafer. We can modulate the potential in the 2DEG on a length-scale given by the width of the doped layer projected onto the facet (<600Å). We have fabricated a one-dimensional (1D) constriction using this technique which exhibits quantized ballistic conductance.