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  Greil, S.M.; Schöpke, A.; Rappich, J.: Strongly Reduced Si Surface Recombination by Charge Injection during Etching in Diluted HF/HNO₃. ChemPhysChem 13 (2012), p. 2982-2988

10.1007/s00393-012-0990-z

Abstract:
In this study, we investigated the behaviour of the surface recombination of light induced charge carriers during the etching of Si in alkaline (KOH) and in acidic etching solutions of HF/HNO₃/CH₃COOH (HNA) or HF/HNO₃/H₃PO₄ (HNP) at different concentration ratios of HF and HNO₃ by means of photoluminescence (PL) measurements. The surface recombination velocity is strongly reduced during the first stages of etching in HF/HNO₃ containing solutions pointing to a well passivated interface by the etching process, where a positive surface charge is induced by hole injection from NO related surface species into the Si near-surface region (back surface field effect). This injected charge leads to a change in band bending by about 150 mV that repulses the light induced charge carriers from the surface and therefore enhances the photoluminescence intensity, since non-radiative surface recombination is reduced.