Bulk GaN-Based Schottky rectifier and UV photodetector

High power switches are indispensable components in electronic subsystems for applications such as advanced hybrid electric vehicles. Due to its unipolar nature, a Schottky diode does not exhibit the minority carrier storage effect, and the device has a negligible reverse current transient. Therefore, faster switching can be achieved with Schottky diodes compared to p-n junction diodes. The successful application of Schottky diodes for power rectification also requires efficient thermal management. In this regard, GaN offers an additional advantage due to its relatively high thermal conductivity (compared to Si). A major disadvantage of sapphire substrates that are widely used for epitaxial growth is the poor thermal conductivity (0.5W/cm-K) which limits high current conduction. Recent studies have shown that high quality, low dislocation density, bulk GaN substrates have a relatively high thermal conductivity of 2.3W/cm-K. Furthermore, it is expected that the bulk GaN substrate allows vertical device geometries with a full backside ohmic contact for much higher current conduction compared to lateral rectifiers fabricated on insulating substrates.