Hydrogen profiling by elastic recoil detection in microcrystalline germanium thin films

The elastic recoil detection technique improved by the time-of-flight is applied to the study of depth inhomogeneities in hydrogenated semiconductor thin films. The ex situ H profiling with a negligible H₂0 surface contamination (H surface peak) is made possible using a 300-A-thick A1 film evaporated on top of the sample. The H depth resolution is about 150 A at the surface and is limited by straggling effects in the bulk. Microcrystalline germanium (/xc-Ge: H) thin films have been obtained at low temperatures (423 and 523 K) from the plasma enhanced chemical vapor deposition using GeH₄ diluted at 0.27% in H₂. An increase of the crystallinity of the juc-Ge: H films vs distance to the substrate is observed. Depending on the deposition temperature, some films show a surface (300 A) H content excess or depletion, attributed to effusion and trapping of molecular hydrogen into internal voids, during the deposition.