Short-range order in amorphous germanium-nitrogen alloys studied by extended x-ray-absorption fine-structure spectroscopy

We present a study of local order in the novel semiconductor alloy a-Ge_1-x{N}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.