THEORY OF INTERFACE-ROUGHNESS SCATTERING IN RESONANT-TUNNELING

We have calculated the effects of interface-roughness scattering on re sonant tunneling through a GaAs-AIxGa1-xAs double-barrier structure. I n our calculation we treat the double-barrier potential exactly. The i nterface-roughness scattering is dealt with nonperturbatively by means of the self-consistent Born approximation, which preserves unitarity. In the presence of scattering, the peak current is reduced by approxi mately 10%, but not more, even though a tunneling electron may be scat tered many times while inside the quantum well. The valley current, on the other hand, is increased by several orders of magnitude due to th e scattering if the barriers are thick enough. For thin barriers, the calculated peak-to-valley (P/V) ratios increase exponentially with the barrier thickness. At a barrier thickness of almost-equal-to 100 angs trom the P/V ratio crosses over to a much slower increase, and eventua lly reaches a maximum, after that the P/V ratio decreases somewhat. Th is qualitative behavior is in good agreement with recent experimental results. A surprising result of this work is that nonperturbative and perturbative calculations give practically identical results for the v alley current for realistic parameter values for the interface roughne ss.