New Kinds of Quantum Wells

The research concentrated almost exclusively on the InAsA1SB quantum well system, with some supporting work on the GaSbA1Sb system. Many advances were made. The overall quality of the quantum wells improved, now routinely yielding room-temperature mobilities of 30,000cm2Vs for 15nm wide wells. A new two-donor model explains the electron concentrations, in terms of a deep EL2- like bulk donor and a mysterious interface donor near the bottom of the well, below the lowest quantum state. A first systematic study of transport properties vs. well widths was undertaken, showing a steep drop in mobility for well widths below 10nm. Cyclotron resonance data taken at the University of Munich give quantitative evidence of non-parabolicity under the combined effect of quantization and band filling. Field effect transistors and photoluminescence data continue to present difficulties. Tilted superlattices TSLs from the GaSbA1Sb system were demonstrated, with very promising properties, as were InAs quantum wells that incorporate GaSbA1Sb TSLs either as corrugated barriers or as periodic center loading. A record electron mobility for InAs 613,000sq.cm Vs was obtained in the corrugated barrier well.