The effects of thermal annealing on oxygen behavior and carrier lifetimes of mc-Si wafers were investigated by means of FTIR and QSSPCD during single step and two step heat treatments in N2 and O2 ambient. It reveals that interstitial oxygen concentration of mc-Si and CZ-Si has a slighter decrease in N2 and O2 ambient during single-step annealing, which means oxygen precipitates are not generated. But oxygen concentration greatly decreases and generates a number of oxygen precipitates during two-step annealing. Bulk lifetime of mc-Si increases in N2 ambient at 850, 950, 1150 ℃ respectively, and annealing in O2 shows better results than that in N2 and annealing in two-step reflected better consequence than annealing in single-step. But lifetime of CZ-Si annealed in N2 or O2 decreases rapidly. The reason of lifetime increase is probably considered due to the fact that interstitial Si atoms of Si/SiO2 interface fill vacancies or some recombination centers at high temperature annealing. Moreover, a number of impurities in mc-Si probably diffuse to grain boundaries so that greatly reduce recombination centers result to lifetime rising.
参考文献
| [1] | Yang DR.;Li DS.;Wang LR.;Ma XY.;Que DL. .Oxygen in Czochralski silicon used for solar cells[J].Solar Energy Materials and Solar Cells: An International Journal Devoted to Photovoltaic, Photothermal, and Photochemical Solar Energy Conversion,2002(1/4):133-138. |
| [2] | Yang DR.;Moeller HJ. .Effect of heat treatment on carbon in multicrystalline silicon[J].Solar Energy Materials and Solar Cells: An International Journal Devoted to Photovoltaic, Photothermal, and Photochemical Solar Energy Conversion,2002(1/4):541-549. |
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