X-VALLEY TUNNELING IN SINGLE ALAS BARRIERS

We examine tunneling through GaAs/AlAs/GaAs single-barrier heterostructures of varying widths using a tight-binding model, including in the calculation for the first time the effects of space-charge regions. Our calculation concentrates on quantities more representative of what one can measure in an experiment than previous efforts and we compare our results to both those earlier tight-binding and pseudopotential-based scattering matrix calculations, none of which include space-charge regions, and results obtained with the more usual envelope-function approach. We find that including the accumulation and depletion layers in the calculation leads to results which are somewhat unexpected in light of the older efforts. Finally, we briefly examine the role of nonzero k(parallel-to) (wave vector parallel to the interface) on tunneling and present current-voltage characteristics for a 10 monolayer barrier structure.