Effective lifetime of minority carriers in silicon: The role of heat- And hydrogen plasma treatments

Results of minority carrier lifetime measurements in different silicon substrates (Cz Si, FZ Si, multi-Si (Baysix)) after heat treatments are presented in this paper. The microwave photoconductivity decay (μ-PCD) method was used for measurements. By using a comparative analysis of high-purity oxygen-free/oxygen-rich FZ Si and also by lifetime measurements of the hydrogenated and non-hydrogenated Cz Si it is established that the presence of both oxygen-related centers and hydrogen leads to a decrease of the minority carrier lifetime in Si. It is concluded that the formation of lifetime killer centers can be attributed in this case to the hydrogen-oxygen-related complexes in Si. At the same time it is established that heat treatments at 450°C lead to the enhancement of the minority carrier lifetime values especially in p-type Cz Si. It is found that the minority carrier lifetime value can be enhanced up to one order of magnitude in this case. It is supposed that this phenomenon can be attributed to the out diffusion of hydrogen from the subsurface region of silicon during heat treatments and also, probably, to the internal gettering of impurities by oxygen-related centers at these temperatures.