Diffusion thermopower due to interface roughness-induced piezoelectric scattering in lattice-mismatched semiconductor quantum wells

Physica E: Low-dimensional Systems and Nanostructures Volume 25, Issue 4, January 2005, Pages 497–503 Cover image Diffusion thermopower due to interface roughness-induced piezoelectric scattering in lattice-mismatched semiconductor quantum wells S.S. Kubakaddia, b, Corresponding author contact information, E-mail the corresponding author, K.R. Usharania, c Choose an option to locate/access this article: Check if you have access through your login credentials or your institution Check access Apply for remote access Purchase $39.95 Show more http://dx.doi.org/10.1016/j.physe.2004.08.097 Abstract We calculate the diffusion thermopower for a degenerate two-dimensional electron gas in real lattice-mismatched semiconductor quantum wells (QWs) at low temperatures. We consider explicitly two scattering mechanisms: (i) the surface roughness-induced piezoelectric effect, a new important scattering source, arising due to a large fluctuating density of roughness-induced piezoelectric charges and (ii) the surface roughness. The scattering parameter pp of energy dependence of the momentum relaxation time and the diffusion thermopower SdSd, of each of the mechanisms separately and also when both the mechanisms are combined, are calculated as a function of electron concentration and well width. The diffusion thermopower, as a function of electron concentration, due to piezoelectric field shows a change in sign for lower concentrations. Interestingly, the diffusion thermopower, due to this mechanism, as a function of well width also shows a change in sign and it is dominant for larger well widths. The numerical calculations are presented for In0.2Ga0.8As/GaAsIn0.2Ga0.8As/GaAs and AlN/GaN QWs. The piezoelectric mechanism is expected to be very important in systems with large piezoelectric constant and lattice mismatch.