Preparation of H-terminated Si surfaces and their characterisation by measuring the surface state density

H-terminated n- and p-type Si(lll) surfaces are characterised by the large-signal field-modulated photovoltage technique (SPV) measuring the surface potential and the energetic distribution of surface states D-it(E). Using aqueous HF acid (HF) and buffered HF solution (BHF), different methods of chemical preparation were carried out characterising the treated surfaces repeatedly during the preparation process. The ideal H-terminated surface displays a very low density of surface states, comparable to well thermally oxidised surface and a significant decrease of HF-induced positive surface charge. The absence of these extrinsic defects indicates the successful preparation of H-terminated surfaces characterised by a nearly intrinsic surface state distribution. The surface state density was found to be mainly influenced by three aspects of the preparation: the doping type and the surface morphology of the substrate, the kind of chemical treatment, and the clean-room conditions as well. Very low surface state density (5 x 10(10) cm(-2) eV(-1) and about 2 x 10(10) cm(-2) eV(-1) on n-type and p-type Si surfaces, respectively) were obtained using BHF as final etching solution, when the treatment was carried out in N-2 atmosphere.