We report on the first observation of surface plasmons at a GaN surface by
high-resolution electron energy loss (HREEL) spectroscopy. Dipole scatterin
g theory using self-consistent electron density profiles is employed to cal
culate the surface energy loss function and hence the expected energy loss
spectra. The characteristic features of both the surface plasmons and the F
uchs-Kliewer (FK) surface optical phonons are well reproduced in the framew
ork of this model. Fitting measured HREEL spectra allows us to give estimat
es of important semiconductor parameters such as electron density, electron
mobility and band bending. Moreover, it is found that the plasmon damping
strongly depends on primary beam energy. Similarly, the FK phonon damping a
nd frequency are also affected by the variation of primary beam energy.