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.