P-type AlN based heteroepitaxial diodes with Schottky, Pin, and junction barrier Schottky character achieving significant breakdown performance

Abstract

The recent achievement of p-type AlN films via Be doping was utilized to achieve novel heteroepitaxial diodes with Schottky, Pin, and junction barrier Schottky (JBS) electrical behavior. Although the heteroepitaxial structures were quasi-vertical, which is subject to many issues lowering the breakdown voltage, the Pin diode achieved a breakdown voltage of ∼25 V for a 200 nm thick unintentionally doped intrinsic layer indicating ∼50% of the theoretical breakdown voltage performance for a similar homoepitaxial GaN pin diode. JBS and Schottky diodes were implemented using the inherent and intentional stress cracking properties of AlN grown on GaN films avoiding regrowth and plasma etching, both known to be technology impediments. The density of the intentional cracks and crystalline quality of the p-AlN films was controlled via Be doping and the total metal dose supplied during the metal modulated epitaxy shutter cycle resulting in differing degrees of grown stress. Since the intentional crack density determines the surface area ratio of the Schottky diode to the Pin diode, it is a key design parameter in optimizing device performance. Furthermore, a novel current spreading layer was implemented to improve the current uniformity in these devices. The high breakdown voltage and good forward voltage characteristics of these devices shows potential to enable high-performance III-nitride high-power devices.