Techniques for Measuring the Composition of Hydrogenated Amorphous Silicon-Germanium Alloys

We grow hydrogenated amorphous silicon-germanium alloys by the hot-wire chemical vapor deposition (HWCVD) technique at deposition rates between 0.5 and 1.4 nm per second. We prepared a set of these alloys to determine the concentrations of the alloying elements as measured by various techniques. This set consists of samples throughout the range of germanium alloying from 0% (a-Si:H) to 100% (a-Ge:H). We find that by making the appropriate calibrations and corrections, our compositional measurements agree between the various techniques. Nuclear reaction analysis (NRA), Fourier transform infrared spectroscopy (FTIR)and secondary ion mass spectrometry (SIMS) all yield similar hydrogen contents, within ±20% for each sample. Electron probe micro-analysis (EPMA) and SIMS yield silicon and germanium contents within ±7% of each other with results being confirmed by Rutherford backscattering (RBS). EPMA oxygen measurements are affected by oxidized surface layers, thus these data show larger O concentrations than those measured by SIMS.