Abstract: A polycrystalline or amorphous substrate having a single crystallilne layer formed thereupon for making a photosensitive detector array and a method for forming the same are disclosed. The single crystalline layer is grown by graphotaxy, i.e. lateral epitaxy, upon the non-single crystalline substrate. A seed crystal of the material which will comprise the layer to be grown is embedded in the substrate. Graphotaxial growth occurs from the seed crystal and travels across the surface of the substrate. Various methods of obtaining graphotaxial growth are disclosed.