Point contact openings in surface passivated macroporous silicon layers

In this paper we demonstrate the preparation of point contact openings in surface passivated macroporous silicon layers. In our experiments we control the etching parameters to vary the percentage of these non-passivated local openings from 0% to 1.6%. We investigate the impact of these local openings in the passivating layer on the effective carrier lifetime. These local openings reduce the measured effective carrier lifetime with increasing percentage of the non-passivated areas. We measure effective carrier lifetimes up to 10 μs on 29 μm-thick fully passivated macroporous silicon samples. We develop and apply a 3-dimensional numerical model to calculate carrier lifetimes as a function of pore morphology, surface recombination, percentage of non-passivated area, and bulk lifetime. The model agrees with the experimental measurements. We find a surface recombination velocity of ( S p a s s = 22.8 − 1.4 + 1.6 ) cm s−1 for the passivated surfaces and Snp= ( 2200 − 1400 + 1500 ) cm s−1 for the non-passivated surface.