INFRARED LUMINESCENCE OF RESIDUAL IRON DEEP-LEVEL ACCEPTORS IN GALLIUM NITRIDE (GAN) EPITAXIAL LAYERS

A characteristic infrared luminescence band, dominated by a zero-phonon line at 1.30 eV has been consistently detected in gallium nitride (GaN) epitaxial layers. It is assigned to the intra-3d-shell transitions T-4(1)(G)-->(6)A(1)(S) of omnipresent iron trace impurities, Fe-Ga(3+)(3d(5)). Another infrared emission is often also observed at 1.19 eV. This is tentatively assigned to chromium trace impurities, Cr-Ga(4+)(3d(2)). The role of iron and chromium as minority-carrier lifetime killers in GaN-based optoelectronic devices is suggested from these data.