10 - Epitaxial Lift-Off for Thin Film Compound Semiconductor Devices

Abstract

This chapter discusses the separation of single crystal thin film epitaxial compound semiconductor layers from a lattice-matched growth substrate, through selective etching, with subsequent bonding of the epilayers onto host substrates. This is a new tool for materials integration which has the potential to produce high performance, low cost integrated assemblies. This separation process, named epitaxial lift-off (ELO), utilizes single crystal device epilayers. Furthermore, thin film device studies indicate that, with proper structural design and processing, thin film devices perform as well as or better than comparable on-wafer unseparated devices. Coupled with the capability for independent optimization of host substrate and thin film device, as well as the reduction in reactance due to the elimination of wirebonds, these thin film integrated systems are a high performance alternative to hybrid packaging. A particularly attractive option that thin film device integration opens to designers is the capability to integrate multiple functions or wavelength devices onto the same host substrate. The main issues yet to be addressed in thin film integration is the reliability of these components and whether the potential cost advantage of this type of integration will be realized.