Tunneling calculations for GaAs-AlxGa(1-x)As graded band-gap sawtooth superlattices

The transmission resonance spectra and tunneling current-voltage characteristics for direct conduction band electrons in sawtooth GaAs-Al _xGa_(1-x)As superlattices are computed. The authors use a transfer matrix method, working within the framework of the effective mass approximation; band nonparabolicity and band-bending at heterojunctions are neglected. Only direct-gap interfaces are considered. It is found that sawtooth superlattices exhibit resonant tunneling similar to that in step superlattices, manifested by correlation of peaks and regions of negative differential resistance in the current-voltage curves with transmission resonances. The step-barrier superlattice always presents some barrier to tunneling, no matter how high the electric field strength