Defect luminescence of nitrogen-doped hydrogenated amorphous germanium thin films

In this letter we report results on photoluminescence (PL) of nitrogen-doped a-Ge:H thin films excited with the 2.4 eV line of an Ar+ laser. The samples were prepared by rf sputtering a c-Ge target in a gaseous mixture of Ar + H-2 + N-2. The PL of samples having an impurity concentration lower than 5 X 10(19) cm(-3) was measured in the 110-180 K temperature range. The emission spectra show a broad band peaking at 0.65 eV, the origin of which is tentatively associated to a negatively charged dangling bond-valence band tail transition. The interpretation is consistent with available data on doping effects in a-Ge:H and with PL data reported in the literature. (C) 1999 Elsevier Science B.V. All rights reserved.