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 vapour deposition and pendeo-epitaxy, while AlGaN/GaN heterostructures were grown using conventional metal organic chemical vapour deposition. 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 −2V (J = 54.5A/cm2) compared to conventionally grown GaN (n = 1.73, J = 117A/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 −2V 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.

Improvement in GaN and AlGaN/GaN Schottky Diode Performance by Reduction in Epitaxial Film Dislocation Density. D.J.Ewing, M.A.Derenge, P.B.Shah, U.Lee, T.S.Zheleva, K.A.Jones: Journal of Vacuum Science & Technology B, 2008, 26[4], 1368-72