Monocrystalline InP Thin Films with Tunable Surface Morphology and Energy Bandgap.

InP is currently being used in various (opto)electronic and energy device applications. However, the high-cost of InP substrates and associated epitaxial growth techniques have been huge impediments for its widespread use. Here, large-area monocrystalline InP thin films are demonstrated via a convenient cracking method, and the InP thin films show material properties identical to their bulk counterparts. Furthermore, the same substrate can be reused for the production of additional InP thin film. This cracking technique is also shown to be a versatile tool to form an ultra-smooth surface or a micro-scale periodic triangular grating structure on the surface, depending on the orientation of the donor substrate used. Strain-induced bandgap energy shift is also observed in localized regions of the thin film with a grating structure. The simplicity of this technique, which does not require any sophisticated equipment and complex fabrication process, is promising to reduce the cost of InP thin film devices.