Minority carrier annihilation property for crystalline silicon surfaces

We report minority carrier recombination effect at cut edges for 520 μm thick p- and n-type silicon substrates coated with thermally grown SiO₂ layers. Samples were mechanically cut to make bare silicon surface edges keeping with other area coated with thermally grown SiO₂. We demonstrate precisely spatial change in minority carrier effective lifetime τ_eff around the cutting edges. 9.35 GHz microwave transmittance measurement system with 635 nm light illumination were used to precisely measure spatial distribution the minority carrier lifetime τ_eff across the cut edges. τ_eff decreased from 3.0×10^-4 and 3.4×10^-3 s (initial) to 4.0×10^-5 and 6.5×10^-4 s at cut edges for p- and n-type samples, respectively. Moreover, decrease in was observed in regions 9 and 8 mm apart from the cut edges for p- and n-type samples, respectively. Those distances were much larger than the minority carrier effective diffusion length. This paper demonstrates and discuss serious carrier annihilation effect caused by the cut edges.