A method and apparatus for forming a super-lattice structure on a substrate is described herein. The super-lattice structure includes a plurality of silicon-germanium layers and a plurality of silicon layers disposed in a stacked pattern. The methods described herein produce a super-lattice structure with transition width of less than about 1.4 nm between each of the silicon-germanium layers and an adjacent silicon layer. The methods described herein include flowing one or a combination of a silicon containing gas, a germanium containing gas, and a halogenated species.