A new two-step phosphorous diffusion gettering process using a sacrificial porous silicon layer was proposed. Due to a decrease in high temperature time, the two-step phosphorous diffusion gettering (porous silicon layer) process weakened the deterioration in performances of porous silicon layers, and increased the capability of impurity clusters to dissolve and diffuse to the gettering regions. By means of the two-step phosphorous diffusion gettering (porous silicon layer) process under conditions of 900C/1h  + 700C/0.5h, the effective lifetime of minority carriers in solar-grade Si was increased to 14.3 times its original value, and the short-circuit current density of solar cells was improved from 23.5 to 28.7mA/cm2, and the . open-circuit voltage from 0.534 to 0.596V along with the transform efficiency from 8.1 to 11.8%, which were much superior to the results achieved by the phosphorous diffusion (porous silicon layer) process at 900C for 1.5h.

A Novel Method to Enhance the Gettering Efficiency in p-Type Czochralski Silicon by a Sacrificial Porous Silicon Layer. C.Zhang, Y.Wang, Z.Wang: Journal of Semiconductors, 2011, 32[3], 032002