We describe a long wavelength infrared detector where an InAs/GaSb superlattice absorber is surrounded by a pair of electron-blocking and hole-blocking unipolar barriers. A 9.9 μm cutoff device without antireflection coating based on this complementary barrier infrared detector design exhibits a responsivity of 1.5 A/W and a dark current density of 0.99×10−5 A/cm2 at 77 K under 0.2 V bias. The detector reaches 300 K background limited infrared photodetection (BLIP) operation at 87 K, with a black-body BLIP D∗ value of 1.1×1011 cm Hz1/2/W for f/2 optics under 0.2 V bias.

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We present a device concept for a spintronic transistor based on the spin relaxation properties a two-dimensional electron gas (2DEG). The device design is very similar to that of the Datta and Das spin transistor. However, our proposed device works in the diffusive regime rather than in the ballistic regime. This eases lithographical and processing requirements. The switching action is achieved through the biasing of a gate contact, which controls the lifetime of spins injected into the 2DEG from a ferromagnetic emitter, thus allowing the traveling spins to be either aligned with a ferromagnetic collector or randomizing them before collection. The device configuration can easily be turned into a memory and a readout head for magnetically stored information.

We apply the D'yakonov-Perel' (DP) formalism to [111]-grown zincblende quantum wells (QWs) to compute the spin lifetimes of electrons in the two-dimensional electron gas. We account for both bulk and structural inversion asymmetry (Rashba) effects. We see that, under certain conditions, the spin splitting vanishes to first order in k, which effectively suppresses the DP spin relaxation mechanism for all spin components. We predict extended spin lifetimes as a result, giving rise to the possibility of enhanced spin storage. We also study [110]-grown QWs, where the effect of structural inversion asymmetry is to augment the spin relaxation rate of the component perpendicular to the well. We derive analytical expressions for the spin lifetime tensor and its proper axes, and see that they are dependent on the relative magnitude of the BIA-and SIA-induced splittings.

We describe a method for computing transmission coefficients for multiband tight-binding bandstructure models. In this method, the transmission probability can be calculated simply by solving a system of linear equations representing the tight-binding form of the Schrodinger equation over a finite region of interest, with specially formulated boundary and inhomogeneous terms to account for the effects of the incoming and outgoing plane-wave states. In addition to being efficient, and simple to implement, our method is numerically stable in treating device structures with large active regions, and therefore capable of modeling realistic band-bending effects. Using this method, we examine transport properties in InAs/GaSb/A1Sb-based interband tunnel structures with a realistic band-structure model. We compare our results with calculations obtained with a two-band model, which includes only the lowest conduction band and the light-hole band. We find that while the primary interband transport mechanism arises from the coupling between the InAs conduction-band states and GaSb light-hole states, in device structures containing GaSb quantum wells, the inclusion of heavy-hole states can introduce additional transmission resonances and substantial hole-mixing effects. These effects are found to have a significant influence on the current-voltage characteristics of interband devices.