Epitaxial lift-off (ELO) is a process technology used to “peel off” thin epitaxial layers from semiconductor substrates through chemical wet etching of a release layer. This process has many economic and performance benefits for compound semiconductor devices. Compared to silicon, compound semiconductor substrates such as GaAs, InP and GaN are orders of magnitude more expensive. After epitaxial growth of the device layers, the substrate is effectively an expensive “handle” for the device structures. ELO allows the epi layers to be removed without damaging the substrate, which can be regrown on many times for considerable cost reduction. The epi layers can be transferred to new, low-cost substrates to improve device performance. For example, at MicroLink Devices we are manufacturing high-efficiency multi-junction solar cells that are highly flexible and lightweight after transferring to a thin metal foil. These solar cells have efficiency greater than 30%, specific power greater than 3000W/kg, and are the ideal technology for powering high-altitude, long-endurance unmanned aerial vehicles (HALE UAVs). Device layers can also be transferred to substrates with improved thermal conductivity for power electronics applications. This presentation will provide an overview of III-V semiconductor ELO technology under development at MicroLink Devices, and discuss present and future commercial applications for this technology.
Dr. Youtsey is the Chief Technology Officer of MicroLink Devices, a company located in Niles, IL that manufactures innovative compound semiconductor materials and devices. He received his PhD at the University of Illinois at Urbana-Champaign, where he pioneered new methods for photo enhanced wet etching of GaN-based materials. After graduation, Dr. Youtsey worked as Process Manager at Nanovation Technologies, a technology startup company specializing in optical components in InP and silica-on-silicon materials. From 2001 to 2007, Dr. Youtsey worked at TriQuint Semiconductor developing distributed feedback (DFB) lasers and VCSELs as well as pHEMT devices based on GaN and GaAs. For the past ten years, his work at MicroLink Devices has focused on transitioning GaAs wafer-scale epitaxial lift-off process technologies from the laboratory to volume production, where it is now used to manufacture lightweight and high-efficiency multi-junction solar cells. Most recently, he has also worked on epitaxial lift-off and layer transfer of GaN materials using bandgap-selective photo enhanced wet etching. Dr. Youtsey is the author of more than 50 journal publications and has received 12 patents.