RESONANT TUNNELING IN POLYTYPE INAS/ALSB/GASB HETEROSTRUCTURES

Polytype heterostructures of GaSb/AlSb/InAs show interband tunneling due to the approximately 0.14 eV overlap of the InAs conduction band and the GaSb valence band. This broken-gap configuration results in several novel mechanisms for negative differential resistance (NDR) that have potential applications in high-speed devices. Double-barrier structures exhibit resonant interband tunneling with high peak-to-valley current ratios due to the resonance enhancement of the tunneling current and the bandgap blocking of the nonresonant current components. Using InAs as the base in a double-barrier polytype heterostructure, resonant tunneling at room temperature through a quantum well as wide as 110 nm has been demonstrated. Also, GaSb/InAs/AlSb/GaSb structures have exhibited interband resonant tunneling with peak-to-valley ratios as high as 20:1 at 300 K and peak current densities up to 28 kA/cm2. In addition to tunneling experiments, Ge and Sn have been shown to be well behaved p-type dopants for GaSb grown by molecular beam epitaxy (MBE), exhibiting free acceptor concentrations as high as 2 x 10(19) and 5 x 10(18) cm-3, respectively.