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Phonon drag thermopower in an AlGaN/GaN heterostructure
Author(s) -
Kubakaddi S. S.
Publication year - 2003
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.200301759
Subject(s) - condensed matter physics , phonon drag , phonon , seebeck coefficient , heterojunction , wurtzite crystal structure , materials science , electron , piezoelectricity , fermi gas , atmospheric temperature range , physics , thermal conductivity , optics , diffraction , quantum mechanics , composite material , meteorology
The theoretical thermopower of a two‐dimensional electron gas (2DEG) is studied in a clean AlGaN/GaN heterostructure of zincblende (ZB) and wurtzite (WZ) symmetry over the temperature range 0.1–10 K. The phonon drag thermopower ( S g ) due to 2DEG coupling with 3D longitudinal and transverse acoustic phonons is calculated for high‐density electrons. It is found that, in both ZB and WZ symmetries, the S g due to piezoelectrically coupled transverse acoustic phonons is dominant over the S g due to longitudinal acoustic phonons via piezoelectric and deformation potential coupling over the entire temperature range. This dominance is attributed to the pronounced piezoelectricity of nitrides and the smaller velocity of transverse acoustic phonons. It is shown that the total S g ∼ T n with n = 3.8 at temperatures T < 2.0 K and is close to n = 4 in the Bloch–Gruneisen limit. Diffusion thermopower ( S d ) is also presented and is found to be significant for T below 0.4 K. The calculations are compared with the results for GaAs/GaAlAs heterostructures.