DEFECT-FREE SINGLE-CRYSTALLINE SIGE NANOMEMBRANES

Silicon-Germanium (Si_1-xGe_x) semiconductor alloys play a pivotal role in the strain engineering of multilayer thin films for microelectronic devices; however, high quality, single crystalline, bulk forms of SiGe do not exist. SiGe thin films can be epitaxially grown on Si substrates, but the lattice constant difference between the two materials results in a compressive strain in the SiGe. If grown thick enough, the strain in the SiGe relaxes via crystalline defects. These defects degrade the material quality of the SiGe and alter the electronic properties. I am going to demonstrate the fabrication of SiGe nanomembranes: fully elastically relaxed, smooth, single-crystalline sheets of SiGe alloy (< ~100nm thick).  The purpose of this research is to develop an efficient method to lift off SiGe from bulk Si substrates while allowing elastic relaxation of the compressive strain in the thin SiGe layer. I will present my methodology, which involves depositing a wax support layer, etching the Si substrate, measuring the strain state of the SiGe layer, and transferring the elastically relaxed SiGe NM to new substrates.