Independently contacted electron–hole gas heterostructures fabricated with focused ion beam doping during molecular beam epitaxial growth

The successful combination of two mature technologies, molecular beam epitaxy (MBE) and focused ion beams into a single, versatile semiconductor growth system has recently been established. It has been shown that the focused ion MBE (FIMBE) system is able to produce spatially selected doping profiles of high quality material in both bulk-doped GaAs and modulation doped GaAs/AlGaAs heterostructures. With the versatility of a Au–Si–Be liquid metal ion source (LMIS), the range of devices that can be produced with three-dimensional topologies has been greatly increased. One such structure is the closely spaced, electron–hole gas heterostructure, which can be easily fabricated, and independently contacted using the FIMBE method. We have fabricated such structures with different barrier widths between the gases, and studied their low-temperature transport properties at various carrier densities. © 1999 American Vacuum Society.