Regrown Vertical GaN p–n Diodes with Low Reverse Leakage Current

Abstract

Vertical c-plane GaN p–n diodes, where the p-GaN layer is formed by epitaxial regrowth using metal–organic chemical-vapor deposition, are reported. Current–voltage (I–V) performance similar to continuously grown p–n diodes is demonstrated, including low reverse leakage current and reverse breakdown voltage in excess of −600 V, despite the lack of field management structures to increase the reverse breakdown voltage. Secondary-ion mass spectrometry analysis of regrown interfaces reveals that the primary source of Si at the regrown interface (“Si spike”) is ex situ contamination during wafer handling prior to loading for regrowth. Continuously grown p–n diodes with intentional Si doping at the p–n junction do not show degraded I–V performance for Si sheet concentrations < 8 × 1011 cm−2. Regrown diodes where the n-type drift layer is (plasma) dry-etched before p-GaN regrowth demonstrate significantly higher reverse leakage current. From these results, we conclude that the presence of Si < 8 × 1011 cm−2 and the epitaxial regrowth process are not responsible for performance degradation. Removal of dry-etch-induced current leakage mechanisms, prior to epitaxial regrowth, should enable a method for selective-area p-type doping control that could lead to realization of high-performance vertical power transistors.