Spectroscopic signatures of native charge compensation in Mg doped GaN nanorods

We study the native charge compensation effect in Mg doped GaN nanorods (NRs), grown by Plasma Assisted Molecular Beam Epitaxy (PAMBE), using Raman, photoluminescence (PL) and X-ray photoelectron spectroscopies (XPS). The XPS valence band analysis shows that upon Mg incorporation the E$_F$-E$_{VBM}$ reduces, suggesting the compensation of the native n-type character of GaN NRs. Raman spectroscopic studies on these samples reveal that the line shape of longitudinal phonon plasmon (LPP) coupled mode is sensitive to Mg concentration and hence to background n-type carrier density. We estimate a two order of native charge compensation in GaN NRs upon Mg-doping with a concentration of 10$^{19}$-10$^{20}$ atoms cm$^{-3}$. Room temperature (RT) PL measurements and our previous electronic structure calculations are used to identify the atomistic origin of this compensation effect.