Implementations of the present disclosure generally relate to methods and apparatus for forming a film on a substrate. More particularly, implementations of the present disclosure relate to methods and apparatus for heteroepitaxial growth of crystalline films. In one implementation, a method of heteroepitaxial deposition of a strain relaxed buffer (SRB) layer on a substrate is provided. The method comprises epitaxially depositing a buffer layer over a dissimilar substrate, rapidly heating the buffer layer to relax the buffer layer, rapidly cooling the buffer layer and determining whether the buffer layer has achieved a desired thickness.