Formation kinetics and extent of the boron oxygen defect in compensated n-type silicon

Abstract

Summary form only given. Combining the low cost of solar grade silicon and the greater immunity to impurities of n-type silicon, boron-phosphorus compensated n-type Cz-grown silicon is a promising material for the photovoltaic industry. However, it has recently been shown to degrade due to boron oxygen (BO) light induced degradation (LID). Lim et al. revealed the slow kinetics, compared to p-type silicon, of both the generation and the annihilation of the defect in compensated n-Si. They also showed that the defect generation and annihilation could not be fitted by a simple exponential function as is the case in p-type silicon. Schutz-Kuchly et al. showed the defect to have a smaller impact on cell efficiency in compensated n-type than in compensated p-type silicon. However much remains to be understood about the boron-oxygen complex formation mechanism in compensated n-type silicon. In particular, the effect of net doping on the defect density remains unclear, although it is essential to determine this in order to assess the suitability of compensated n-type Cz-Si for solar cell fabrication. In this paper we present new data regarding the formation kinetics and extent of the boron oxygen complex in compensated n-type silicon. The influence of the excess carrier density on the boron oxygen defect generation rate in n-type silicon is explicitly investigated. We also show the effect of the net doping on the kinetics of the BO formation, and on the defect density, with surprising results. Finally we explore the effect of thermal processes on the defect density.