Optical and electronic properties of reactively sputtered amorphous GeNx:H

Basic photoelectronic properties of hydrogenated amorphous germanium nitride (a-GeNx:H) are presented for the first time. Amorphous-GeNx:H films were prepared by an rf reactive sputtering of a Ge target using Ar+N2+H2 mixed gases and their optical band gaps were controlled continuously in the range from 1.0 to 3.3 eV by varying the compositional ratio of nitrogen to germanium. In contrast to H-free a-GeNx, the temperature dependence of the dark conductivity of a-GeNx:H shows that thermally activated band conduction prevails in the carrier transport over a wide temperature range at least down to 180 K. The photo-to-dark conductivity ratio under AM1 light of unoptimized a-GeNx:H amounts to 40.