title: Strongly reduced Si surface recombination by charge injection during etching in diluted HF/HNO3.
abstract: Herein, we investigate the behaviour of the surface recombination of light-induced charge carriers during the etching of Si in alkaline (KOH) and acidic etching solutions of HF/HNO(3)/CH(3)COOH (HNA) or HF/HNO(3)/H(3)PO(4) (HNP) at different concentration ratios of HF and HNO(3) by means of photoluminescence (PL) measurements. The surface recombination velocity is strongly reduced during the first stages of etching in HF/HNO(3)-containing solutions pointing to a interface well passivated 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.
authors: Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Institut für Si-Photovoltaik, Kekuléstr. 5, 12489 Berlin, Germany. stefanie.greil@helmholtz-berlin.de
authors: Stefanie M
authors: SM
authors: Greil
authors: Andreas
authors: A
authors: Schöpke
authors: Jörg
authors: J
authors: Rappich