Thermal Desorption Spectroscopy of Hydrogen from Amorphous Hydrogenated Silicon

T h e r m a l desorption spectroscopy (TDS) based on the mass spectroscopy of thermal ly evolved hydrogen is used for desorption analysis of amorphous hydrogenated silicon (a-Si:H). Two series of glow discharge chemical vapour deposited a-Si:H were investigated by the T D S method . Cons tan t t e m p e r a t u r e growth ra te enabled to determine t empera tu re regions of hydrogen evolution and its to ta l content in the film. These values are compared with the results of infrared (IR) absorpt ion spectroscopy. T h e dependence of the H content and the position of t he m a x i m u m of t he evolution curve on deposit ion conditions, as radio frequency (RF) power used in a s t anda rd p lasma enhanced chemical vapour deposit ion ( P E CVD) glow discharge, was observed. T h e R F power was related to a silane flow ra te dur ing the deposit ion. The lower t empe ra tu r e of t he evolution peaks and simultaneously the lower H content were observed in the layers prepared under t he larger relative R F power conditions ( the high silane decomposition efficiency). These results correlate well with light degradat ion measurements in device quality samples.