Effect of Thermal Strain and Carrier Concentration in the Phonon Frequencies of GaN

摘要

Electron-phonon interactions in wurtzite GaN epitaxial films grown on sapphire substrates have been investigated by spatially resolved micro-Raman scattering and Hall measurements. Frequency shifts of longitudinal, transversal and non-polar optical phonons have been explored with respect to plasmon-coupling, energy renormalization and strain. LO phonon-plasmon coupling is applied for electron density and mobility estimates yielding a slight anisotropy of the mobilities of about #mu#_(e,planar)/#mu#_(e,axial)=0.8+-0.2. The interaction of hole plasmons with LO phonons is finally discussed.