Fabrication and Electrical/Optical Characterization of Bulk GaN-based Schottky Diodes

Abstract

As a wide bandgap semiconductor material, Gallium Nitride has long been considered as promising in blue and UV Light Emitting Diodes. And recently, its great potential in high power and high temperature applications is another area gaining lots of attention. Thanks to the fast development of crystal growth technology, high quality bulk Gallium Nitride substrate became available by Hydride Vapor Phase Epitaxy technique, which can greatly simplify fabrication process. With a fast switching speed and a low forward drop, Schottky diode is useful in high power electronic. Therefore, in this dissertation, the fabrication and characterization of Schottky diode based on bulk Gallium Nitride is discussed. In order to achieve high breakdown voltage, while still keeping high forward current, vertical Schottky diodes were fabricated on low doping GaN epilayer grown on high doping bulk GaN substrate all by low cost HVPE. Device performance is discussed. Reliability of high power devices is always an issue. Self-heating is one of the concerns that limits the performance and lifetime of GaN devices. It is of great importance to monitor temperatures, especially when the devices are under operation. Raman spectroscopy offers the non-contact way method to diagnosis temperature. Therefore, it was used to probe Schottky diode temperature when the device was biased. Chemical stability of GaN makes it tolerant to harsh environment, such as high radiation. Diode degradation was observed after gamma ray irradiation, which gave information about intrinsic defects in GaN.