Challenges and Opportunities in GaN and ZnO Devices and Materials

This special issue spawned from mainly the motivation used by the scientific community in regard to potential applications of ZnO to electronic and optoelectronic devices which seemingly are centering about device applications already addressed by GaN to a large extent. The late Dr. Cole W. Litton (Fig. 1) successfully made the case that a small group of experts in both the GaN and ZnO communities be brought together for a probing discussion which would then lead to a report which manifested itself as this special issue. Because of his uncanny vision and relentless effort in convincing Dr. D. J. Silversmith of the Air Force Office of Scientific Research to fund such a meeting and convincing already overly committed H. Morkoç to host the meeting in Richmond, VA, October 18Y20, 2007, this special issue is dedicated to the memory of Dr. Litton. Facilitated by scene setting presentations, the topics discussed included bulk GaN and ZnO, defects, p-type doping paradox, particularly for ZnO, promising heterostructures and devices based on ZnO, ferromagnetism in GaN and ZnO, doping of high mole fraction AlGaN and InGaN, particularly p-type, light extraction and efficiency in GaN-based light-emitting diodes (LEDs), degradation mechanisms in GaN-based lasers and heterojunction field-effect transistors (HFETs) and potential measures to enhance lifetime and performance, negative differential resistance in GaN-based heterostructures, and intersubband transitions. This special issue addresses to a large extent the aforementioned subjects deemed critical to both the GaNand ZnO-based technologies. This special issue addresses to a large extent the challenges and opportunities in GaN and ZnO devices andmaterials deemed critical to both the GaNand ZnO-based technologies.