This book differs from previous volumes on wide bandgap semiconductors in that the emphasis is specifically on materials aspects related to electronic properties and devices. Solid advances are reported in the growth techniques of all three materials groups. In particular, the critical importance of surfaces, interfaces, doping, defects and impurities is demonstrated. Potential device applications ranging from new high-frequency, high-power all-solid-state devices to unique cold-cathode electronic devices are presented. Whilst the results demonstrate real promise for a wide range of new solid-state devices that are not feasible with current production materials, it is also evident that substantial progress in materials research is needed to fulfill the real potential of these applications. Critical issues related to the electronic potential of all three materials are addressed. Topics include: device technologies - devices, metallizations, etching, and implantation; bulk and bulk-like crystal growth; film growth; defects and structural properties; doping and electrical properties and optical and field-emission properties.