Band structure engineering for electron tunneling in heterostructures

Summary form only given. It has been shows that inelastic tunneling via the AlGaAs X minimum is responsible for the excess valley current in GaAs/AlGaAs resonant tunneling devices. In addition, negative differential resistance has been observed in GaAs/AlAs/GaAs single-barrier heterostructures, due to the presence of a quasi-bound state associated with the X-point profile. This surprising result is due to the fact that, although the Gamma -point profile of this heterostructure is a simple single tunneling barrier, the X-point profile actually constitutes a quantum well some 0.3 eV deep lying about 0.2 eV above the Gamma -point of GaAs. Another way to realize single-barrier devices with negative differential resistance is based on tunneling below the midgap. In this case, the barrier transmission probability decreases with applied bias because the decay constant increases toward the middle of the bandgap. Room-temperature observations of this type of negative differential resistance were made. Peak-to-valley ratios of 1.6:1 are seen in InAs/AlGaSb single-barrier devices exhibiting this phenomenon.