SiGe layer structures for solar cell application grown by liquid phase epitaxy

Si_1-xGe_x layers with x=0.09-0.27 were grown on Si (111) substrates by liquid phase epitaxy (LPE). The formation of dislocations caused by the lattice mismatch was reduced from 5×10 ⁷ to 7×10⁵ cm^-2 by growing buffer layers in which the Ge content increased continuously from 4 at% Ge at the substrate/buffer interface up to the Ge content of the Si_1-x Ge_x base layer. The p-type SiGe layers grown from indium solution are about 20 μm thick. The carrier concentration of 5×10¹⁶-2×10¹⁷ cm^-3 depends on Ge content and Ga doping. With a thin-film cell processed from a 14 μm thick LPE-grown Si_0.9Ge_0.1 base layer, an efficiency of 9.1% was achieved even without the presence of a buffer layer