Active doping of B in silicon nanostructures and development of a Si quantum dot solar cell

摘要

Active doping of B was observed in nanometer silicon layers confined in SiO_2 layers by secondary ion mass spectrometry (SIMS) depth profiling analysis and confirmed by Hall effect measurements. The uniformly distributed boron atoms in the B-doped silicon layers of [SiO_2 (8nm)/B-doped Si(10nm)]_5 films turned out to be segregated into the Si/SiO _2 interfaces and the Si bulk, forming a distinct bimodal distribution by annealing at high temperature. B atoms in the Si layers were found to preferentially substitute inactive three-fold Si atoms in the grain boundaries and then substitute the four-fold Si atoms to achieve electrically active doping. As a result, active doping of B is initiated at high doping concentrations above 1.1 × 10~(20)atomscm~(- 3) and high active doping of 3 × 10~(20)atomscm~(- 3) could be achieved. The active doping in ultra-thin Si layers was implemented for silicon quantum dots (QDs) to realize a Si QD solar cell. A high energy-conversion efficiency of 13.4% was realized from a p-type Si QD solar cell with B concentration of 4 × 10~(20)atomscm~(- 3).