TRANSPORT STUDIES AND INFRARED-SPECTROSCOPY ON ALAS/GAAS MIS HETEROJUNCTIONS WITHOUT DOPANTS IN THE BARRIER

Novel AlAs/GaAs heterostructure insulated-gate field-effect transistors are fabricated that allow a high-mobility two-dimensional electron gas (2DEG) to be generated at an interface close to the device surface without intentional doping in the barrier. The 2DEG is field-effect-induced via a front gate and the carriers are extracted from a back contact far below the 2DEG grown as a saturation-doped layer in the buffer. We investigate the low-temperature electronic properties of these devices with quasi-static magnetotransport experiments as well as far-infrared (FIR) transmission spectroscopy. The experimental results are discussed in view of intriguing new aspects for mesoscopic electron systems, where investigations of large arrays of periodic structures in conventional modulation-doped heterojunctions are hampered by potential fluctuations and threshold variations. FIR transmission spectra of wire arrays prepared in such samples demonstrate the suitability of the device concept for laterally microstructured systems.