Minority Carrier Annihilation in Lateral Direction Caused by Recombination Defects at Cut Edges and Bear Surfaces of Crystalline Silicon

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We report on the photo-induced minority carrier annihilation effect in the lateral direction caused by cut edges and partially formed bare surfaces for 500-μm-thick n-type silicon substrates coated with thermally grown SiO<inf>2</inf>layers. A 9.35 GHz microwave transmittance measurement system with illumination with a 0.2-cm-wide 635-nm continuous wave light beam was used to measure spatial distribution of the minority carrier effective lifetime \tau_{\text{eff}}. A mechanical cut decreased \tau_{\text{eff}} in a 0.9-cm-wide region from the cut edges. \tau_{\text{eff}} decreased from 3.4\times 10^{-3} (initial) to 6.5\times 10^{-4} s at cut edges. A simple model of carrier diffusion in the lateral direction with a carrier lifetime of 3.4\times 10^{-3} s and a recombination velocity of 500 cm/s at the cut edges well explained the experimental spatial change in \tau_{\text{eff}} near the cut edges. A similar widely spatial decrease in \tau_{\text{eff}} was also observed in the region coated with thermally grown SiO<inf>2</inf>layers near the bare silicon surface formed by partial etching of SiO<inf>2</inf>.
2013-04-25