High-Frequency Applications of Resonant-Tunneling Devices

摘要

Since the prediction (Kazarinov and Suris, 1971; Tsu and Esaki, 1973) and firstobservation (Chang et al.,1974) of resonant tunneling through double-barrier heterostructures, there has been increasing interest in the field. This renewed interest arises in part because of the advances in the ease of fabrication by molecular beam epitaxy (MBE) of the atomically thin structures required, and in part because the charge transport process has been shown to be extremely fast (Sollner et al., 1983). The quality of the heterostructure interfaces in the GaAS/AlAs system has been improved to the point that peak to valley (P/V) ratios of 3-4 at room temperature (Shewchuck et al.,1985; Goodhue et al.,1986) and nearly 10 at 77 K are easily achieved with current densities well above 10000 A/sq cm. New material systems have been explored by several groups, the most notable being InGaAs lattice-matched to InP substrates with AlAs barriers. The Fujitsu group first showed the great promise of this material (Inata et al.,1987), and the best published results give a P/V ratio of about 30 at 300 K (Broekaert and Fonstad, 1988).