Properties of silicon oversaturated with implanted hydrogen

Abstract

Structural properties of silicon layers oversaturated with implanted hydrogen (up to 20%) are studied by means of IR Fourier spectroscopy, Raman spectroscopy, and high-resolution electron microscopy (HREM). The data obtained by the different methods are found to agree fairly well with one another. Silicon samples implanted up to fluxes (1–3)×10 17 cm −2 reveal a layered structure. It is found that just after implantation a surface layer forms which manifests the properties of amorphous silicon. During subsequent heat treatments at 600–800 °C, amorphous layers with embedded silicon nanocrystals form, with a simultaneous decrease in the degree of polymerization of SiH bonds and hydrogen transition in a molecular form. Results of electrical studies of the hydrogenated silicon layers allow us to put forward a new production method for Si:H/c-Si heterostructures based on implanted H which is promising for photoelectrical converters. The new technology makes it possible to avoid the stage of deposition of amorphous silicon from ecologically harmful compounds. The density of states both in the amorphous silicon and at the Si:H/c-Si interface is of the order 5×10 17 cm −3 and it is compared to CVD technology.