Spectroscopic signatures of native charge compensation in Mg doped GaN Nanorods

TL;DR

This study investigates native charge compensation in Mg-doped GaN nanorods using spectroscopic techniques, revealing significant native charge compensation and its dependence on Mg concentration, with implications for optoelectronic properties.

Contribution

It provides a detailed spectroscopic analysis of native charge compensation in Mg-doped GaN nanorods and quantifies the compensation effect at high Mg concentrations.

Findings

Native charge compensation reduces the Fermi level by ~2 eV.

Raman LPP mode is sensitive to Mg concentration and carrier density.

Two orders of native charge compensation observed at high Mg doping levels.

Abstract

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.