Properties of Ga 1− x Mn x N epilayers grown by plasma-assisted molecular beam epitaxy using Raman spectroscopy

Abstract

Raman spectroscopy has been used to study the lattice properties of plasma-assisted molecular beam epitaxy grown Ga 1− x Mn x N layers ( x = 0–12%). Raman spectra corresponding to the intrinsic GaN layers demonstrate three Raman active excitations at 144, 570 and 729 cm −1 identified as E 2 L , E 2 H and A 1(LO), respectively. The Mn-doped GaN layers exhibit additional excitations attributed to defect-activated Raman scattering (DARS) and Mn x –N related frequency modes in the vicinity of E 2 H mode. The observed frequencies associated with Mn x –N modes are in fair agreement with the standard theoretical results. Based on line shape fitting analysis, apparent free carrier concentrations in Ga 1− x Mn x N layers, involving LO phonon–plasmon coupled (LOPC) mode are found in the range of 1.6 × 10 17 to 1.1 × 10 18 cm −3. The ferromagnetic character of the layers is discussed in view of the estimated carrier density.