We present a study of local order in the novel semiconductor alloy a-${\mathrm{Ge}}_{1\mathrm{-}\mathrm{x}}$${\mathrm{N}}_{\mathrm{x}}$:H using extended x-ray-absorption fine structure (EXAFS) at the Ge K edge. We find that the first coordination shell is composed of Ge and N, the relative importance of which varies with the total N concentration. A careful analysis also allowed us to identify a second-shell contribution due to Ge atoms linked to the central Ge via N. All mean interatomic distances were found to be independent of nitrogen concentration. By measuring the mean-square relative fluctuation of the second-shell interatomic distance we give an upper limit to nitrogen bond-angle fluctuations, providing the first such determination by EXAFS in amorphous semiconductor alloys.

• Received 24 October 1988

DOI:https://doi.org/10.1103/PhysRevB.39.8364