This program will focus on low temperature, photo-enhanced chemical vapor deposition techniques to achieve single crystal epitaxy. Non- selective photo-excitation using a low pressure mercury lamp, as well as selective epitaxy using an ArF excimer laser will be used coupled with rapid thermal processing using incoherent arc lamps to rapidly adjust the substrate temperature during growth. Two materials systems to be studied using this growth technique include silicon N- i-P-i doping superlattices and Si-SixGe1-x strained layer superlattices/pseudomorphic layers. These systems will be examined from the viewpoint of novel device applications. They are, respectively, electroptic modulation using the tunable bandgap properties of N-i-P-i superlattices and the possibility of obtaining direct bandgap superlattices using a combination of Brillouin zone folding and lattice strain in the Si-SixGe1-x strained layer system. We believe a photo-enhanced CVD technique has significant potential advantages over competing growth techniques. It does not require ultra high vacuum conditions as in MBE. It allows selective excitation of precursor species, allowing better crystalline quality with less contamination than plasma-CVD. Substrate temperatures can be lowered compared to MOCVD. In conclusion, excellent heterostructures with abrupt interfaces and doping profiles should be achievable by photo-enhanced CVD to allow novel device applications using compositional and doping superlattices.
