Strongly Reduced Si Surface Recombination by Charge Injection during Etching in Diluted HF/HNO3

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/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 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. The bends: The surface recombination of light‐induced charge carriers during the etching of Si is investigated by means of photoluminescence measurements (see picture). The surface recombination velocity is strongly reduced during the first stages of etching, pointing to a interface well passivated by the etching process.