Perpendicular electronic transport in doping superlattices

Electronic transport measurements are performed at 77 and 300 K on doping superlattices in perpendicular direction to the quantum well planes. The periods of the doping superlattices range from 150 to 600 Å. The current-voltage characteristics in long period doping superlattices (type B) are strongly nonlinear and exhibit a new type of negative differential conductivity. The occurrence of negative differential conductivity is caused by avalanche multiplication in the high-field regions of the superlattice and accumulation of holes in the valence-band maxima. In short period doping superlattices (type A) the current-voltage characteristics are linear at temperatures of 300 and 77 K showing that tunneling through thin barriers dominates perpendicular transport. The calculation of the tunneling current yields a strong dependence on the period (exp−z3/2p).