  We have performed an $in$-$situ$ depth profile study of Mn-doped GaN prepared
by a low temperature thermal diffusion method using photoemission and x-ray
absorption spectroscopy. It was revealed from the core-level photoemission
measurements that Mn ions are diffused into a deep ($\sim$ 70 \AA) region of
the GaN substrates and that the line shapes of Mn 3$d$ partial density of
states obtained by resonant photoemission measurements was close to that of
Ga$_{1-x}$Mn$_x$N thin films grown by molecular-beam epitaxy. From x-ray
absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD)
measurements at the Mn $L$-edge, it was revealed that the doped Mn ions were in
the divalent Mn$^{2+}$ state and primarily paramagnetic. In magnetization
measurements, weak hysteresis was detected in samples prepared using $p$-type
GaN substrates while samples using $n$-type GaN substrates showed only
paramagnetism.
