Embodiments of the invention as recited in the claims relate to thin film multi-junction solar cells and methods and apparatuses for forming the same. In one embodiment a method of forming a thin film multi-junction solar cell over a substrate is provided. The method comprises positioning a substrate in a reaction zone, providing a gas mixture to the reaction zone, wherein the gas mixture comprises a silicon containing compound and hydrogen gas, forming a first region of an intrinsic type microcrystalline silicon layer on the substrate at a first deposition rate, forming a second region of the intrinsic type microcrystalline silicon layer on the substrate at a second deposition rate higher than the first deposition rate, and forming a third region of the intrinsic type microcrystalline silicon layer on the substrate at a third deposition rate lower than the second deposition rate.