Method of creating improved material quality, suspended material structures on lattice-mismatched substrates for MEMS and photonics applications

Stanford researchers have improved material quality and suspension of micro- and nanostructures on lattice-mismatched substrates. Epitaxial growth of material on a lattice-mismatched substrate typically results in a large amount of defects due to misfit dislocations and threading dislocations that can greatly reduce performance. Typically, one can reduce the number of defects through continued growth and thermal annealing, forming a buffer layer upon which a desired structure of high material quality is grown. However, several applications require the removal of the defective regions of the buffer layer while protecting the desired structure, even if the buffer material and the structure are composed of the same or similar materials. This invention presents a method for removal of the defective buffer layer while creating a suspended structure by defining an etch-stop layer between the buffer layer and the desired structure. The process is entirely bottom-up growth with top-down fabrication requiring no wafer bonding or transfer process steps.