Hydrogen profiling in amorphous silicon films and p-n junctions

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Abstract
Hydrogen depth profiles, obtained by a nuclear reaction technique, have been investigated in a series of glow-discharge deposited Si specimens. These include undoped films, homogeneously doped n- and p-type specimens, junctions and continuously graded devices. It is shown that the hydrogen concentration CH in the bulk of the specimens depends systematically on the doping level and thus on the position of the Fermi energy ∊F in the mobility gap. In junctions there exists an almost linear dependence of Ch on (∊c-∊f)o, extending over a range of about 6 at.%. The lowest values of CH (1-2 at.%) occur in p+ regions. The results are discussed and it is suggested that, with the good depth resolution obtainable, hydrogen profiling may be a useful approach for the study of barrier profiles in a-Si devices. In addition to the bulk effects, the doping dependence of CH at the surface and the specimen-substrate interface has been investigated.