Extremely low surface recombination velocities in black silicon passivated by atomic layer deposition

We investigate the optical and opto-electronic properties of black silicon (b-Si) nanostructures passivated with Al2O3. The b-Si nanostructures significantly improve the absorption of silicon due to superior anti-reflection and light trapping properties. By coating the b-Si nanostructures with a conformal layer of Al2O3 by atomic layer deposition, the surface recombination velocity can be effectively reduced. We show that control of plasma-induced subsurface damage is equally important to achieve low interface recombination. Surface recombination velocities of Seff<13 cm/s have been measured for an optimized structure which, like the polished reference, exhibits lifetimes in the millisecond range.