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 high4 T sub1 (G) to high6 A sub1 (S) of omnipresent iron trace impurities, Fe high3plus/subGa (3d high5). Another infrared emission is often also observed at 1.19 eV. This is tentatively assigned to chromium trace impurities, Cr high4plus/subGa (3d high2). The role of iron and chromium as minority-carrier lifetime killers in GaN-based optoelectronic devices is suggested from these data.