Nicholas E. Grant1,2, В. П. Маркевич3, Jack Mullins3, А. R. Peaker3, Fiacre Rougieux2, Daniel Macdonald2
1Phone: +44 247 652 8590
2Research School of Engineering, College of Engineering and Computer Science, Australian National University, Canberra ACT 2601, Australia
3Photon Science Institute and School of Electrical and Electronic Engineering, University of Manchester, Manchester M13, United Kingdom
Tóm tắt
By studying the minority carrier lifetime in recently manufactured commercially available n‐ and p‐type float‐zone (FZ) silicon from five leading suppliers, we observe a very large reduction in the bulk lifetime when FZ silicon is heat‐treated in the range 450–700 °C. Photoluminescence imaging of these samples at the wafer scale revealed concentric circular patterns, with higher recombination occurring in the centre, and far less around the periphery. Deep level transient spectroscopy measurements indicate the presence of recombination active defects, including a dominant center with an energy level at ∼Ev + 0.5 eV. Upon annealing FZ silicon at temperatures >1000 °C in oxygen, the lifetime is completely recovered, whereby the defects vanish and do not reappear upon subsequent annealing at 500 °C. We conclude that the heat‐treatments at >1000 °C result in total annihilation of the recombination active defects. Without such high temperature treatments, the minority carrier lifetime in FZ silicon is unstable and will affect the development of high efficiency (>24%) solar cells and surface passivation studies.
