Properties of Ga1−x Mnx N epilayers grown by plasma-assisted molecular beam epitaxy using Raman spectroscopy

Raman spectroscopy has been used to study the lattice properties of plasma-assisted molecular beam epitaxy grown Ga1−x Mnx 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 E2L, E2H and A1(LO), respectively. The Mn-doped GaN layers exhibit additional excitations attributed to defect-activated Raman scattering (DARS) and Mnx–N related frequency modes in the vicinity of E2H mode. The observed frequencies associated with Mnx–N modes are in fair agreement with the standard theoretical results. Based on line shape fitting analysis, apparent free carrier concentrations in Ga1−x Mnx N layers, involving LO phonon–plasmon coupled (LOPC) mode are found in the range of 1.6 × 1017 to 1.1 × 1018 cm−3. The ferromagnetic character of the layers is discussed in view of the estimated carrier density.