Passivation of thermally-induced defects with hydrogen in float-zone silicon

In this study, passivation of thermally-activated recombination centers with hydrogen in n-type float zone (FZ) Si containing nitrogen has been investigated. Prior to hydrogenation samples were heated to 550 °C using rapid thermal annealing and conventional furnaces. A large decrease in minority carrier lifetime occurred upon the heat-treatments confirming previous reports. A sequence of electron traps created in this process have been detected in the deep level transient spectra and characterized. Significant changes in the spectra have occurred after treatments in remote hydrogen plasma and subsequent annealing of the hydrogenated samples in the temperature range 100 °C-400 °C. A total elimination of electrical activity of the thermally induced defects has been observed in the hydrogenated samples subjected to annealing in the temperature range 150 °C-300 °C. The results obtained suggest a simple way for an effective cure of the degraded FZ-Si-based solar cells. Possible defect reactions occurring in the FZ-Si crystals and the role of nitrogen and carbon upon the performed treatments are discussed.