Improvement in GaN and AlGaN/GaN Schottky diode performance by reduction in epitaxial film dislocation density

Abstract

The electrical characteristics of AlGaN/GaN heterostructures and GaN Schottky diodes were correlated with dislocations and other material defects. GaN epitaxial films were grown using conventional metal organic chemical vapor deposition (MOCVD) and pendeo-epitaxy, while AlGaN/GaN heterostructures were grown using conventional MOCVD. Current-voltage (I-V) measurements displayed a wide variation in ideality factor and reverse leakage current density. Schottky diodes fabricated on the pendeo-epitaxial material displayed improved ideality factor (n=1.35) and leakage current density measured at −2 V (J=54.5 A/cm2) compared to conventionally grown GaN (n=1.73,J=117 A/cm2). The electrical properties of the Schottky diodes on the AlGaN/GaN heterostructure varied across the sample, showing no spatial dependence. Ideality factor and Schottky barrier height ranged n=1.6−3.0 and ϕB=0.69−0.87, respectively. Reverse leakage current density at −2 V varied by up to three orders of magnitude. Etch pit density and atomic force microscopy revealed three orders of magnitude reduction in dislocation density for the pendeo-epitaxial GaN compared to conventional GaN, while cathodoluminescence indicated lower defect density for the pendeo-epitaxial GaN. Etch pit density revealed almost an order of magnitude lower dislocation density beneath those diodes with improved characteristics on the AlGaN/GaN heterostructure.