Electronic properties in p-type GaN studied by Raman scattering

Raman spectra from p-type GaN have been systematically studied in the hole density range of ${\text{5×10}}^{16}{\text{–1×10}}^{18}\hspace{0.17em}{\mathrm{cm}}^{\mathrm{-3}}.$ Contrary to the case of n-type samples, spectral profiles of the LO-phonon-plasmon coupled mode in p-type show no remarkable change with the hole density. Thus, precise evaluation of electrical transport parameters such as carrier density and mobility from the coupled mode profile is difficult. However, a continuum band has been observed in the low-frequency range of the spectra, becoming intense with the increase of the hole density. This band has been attributed to the inter-valence-band transition of holes, and the intensity can be used as a good measure of the hole density.