Large room-temperature effects from resonant tunneling through AlAs barriers

Abstract

At room temperature, we have observed negative differential resistance in AlAs double-barrier structures and a large hysteresis in the current-voltage characteristic of a stack of five AlAs double-barrier structures. The peak-to-valley ratio of the current was as high as 3.5:1 in a double-barrier structure. To the best of our knowledge, this is the largest room-temperature peak-to-valley ratio observed to date in a double-barrier structure and the first report of a room-temperature hysteresis in a stacked structure. These structures were grown by molecular beam epitaxy using thin AlAs barriers in GaAs. Both the first and second resonances were observed, and are well explained by simple tunneling theory assuming a value of 1.0±0.1 eV for the GaAs-AlAs conduction-band discontinuity seen by the tunneling electrons. This value is very close to the difference in conduction-band energy at the Γ points found by using the accepted values of GaAs and AlAs band gaps with 65% of the band-gap difference appearing in the conduction band. This suggests that negligibly few electrons relax to the lower AlAs X valley as they tunnel through the 1.5–2.5-nm-thick AlAs barriers. These results indicate that AlAs should be a high quality barrier material for a variety of heterojunction devices.