The diffusion thermopower Sd of the 2-dimensional electron gas at a GaN/AlGaN heterojunction was studied, in detail, in the low-temperature region T<30 K. The important mechanisms of scattering of electrons considered were those by edge dislocations, remote and background impurities, interface charges and roughness, and bulk acoustic phonons via deformation potential and piezoelectric fields. The dominant contribution to Sd was found to be from dislocations via the coulomb interaction; the contribution from strain field associated with the dislocations is, comparatively, small. The contribution from acoustic phonons was negligible. The calculations, for pure samples without dislocations in the low-temperature region where acoustic phonon scattering dominates, bring out the characteristics of the Bloch-Grüneisen regime, as in mobility studies.

Low-Temperature Diffusion Thermopower in GaN/AlGaN Heterojunctions - Effect of Dislocations. M.D.Kamatagi, N.S.Sankeshwar, B.G.Mulimani: Physical Review B, 2005, 71[12], 125334 (7pp)