Wacker, Andreas1; Jauho, Antti-Pekka2; Zeuner, S.3; Allen, S. K.3
1 Department of Micro- and Nanotechnology, Technical University of Denmark2 Center for Nanostructured Graphene, Center, Technical University of Denmark3 University of California, Santa Barbara
We report a combined theoretical and experimental study of electrical transport in weakly coupled doped superlattices. Our calculations exhibit negative differential conductivity at sufficiently high electric fields for all dopings. In low-doped samples the presence of impurity bands modifies the current-voltage characteristics substantially, and we find two different current peaks whose relative height changes with the electron temperature. These findings can explain the observation of different peaks in the current-voltage characteristics with and without external THz irradiation in low-doped samples. From our microscopic transport model we obtain quantitative agreement with the experimental current-voltage characteristics without using any fitting parameters. Both our experimental data and our theory show that absolute negative conductance persists over a wide range of frequencies of the free-electron laser source.
Physical Review B (condensed Matter and Materials Physics), 1997, Vol 56, Issue 20, p. 13268-13278