Incorporation of Cu and Al in Thin Layer Silicon Grown from Cu-Al-Si

Cu and Al concentrations in silicon thin layers grown from Cu-Al-Si are determined by segregation at the solid-liquid interface, and for the fast diffusing Cu, also at the free silicon surface. Using the multicomponent regular solution model and experimental results, we found that Si-Al and Si-Cu interactions in the liquid solution are repulsive, and Al-Cu interaction is attractive. As a result,Al incorporation as a function of Cu and Al compositions in the growth solution is determined at about 900.deg.C. Up to 0.2 .OMEGA..cntdot.cm P-type resistivities caused by Al doping are achieved because of suppression of Al incorporation by Cu, yet with a substantial amount of Al still present in the liquid for substrate surface-oxide removal. On the other hand, Cu concentration in the grownlayers is reduced by Al in the liquid during growth and by surface segregation after growth. The surface segregation phenomenon can be conveniently used to getter Cu from the bulk of silicon layers so that its concentration (.appx.10.sup.16 cm-3) is much lower than its solubility (2.5x10.sup.17 cm-3) at the layer growth temperature and the reported 10.sup.17 cm-3 degradation onset for solar-cellperformance.