Physical and electrical characterizations of low n-doped MOCVD GaN-on-sapphire layers for power electronics applications

• Fabrication of uniformly low n-doped (1.4 – 5.5 × 10 15 cm -3 ) MOCVD GaN-on-sapphire layers and quasi-vertical Schottky barrier diodes (SBDs). • Raman spectroscopy is proven to be a promising tool to analyze n-carrier concentration variation for biaxial stressed GaN layers. • Analysis of the effects of surface defects on direct and reverse current characteristics of SBDs. • Forward and reverse current characteristics of most fabricated SBDs are comparable to some of the best vertical GaN-on-GaN SBDs. This work presents physical and electrical characterizations of low n-doped MOCVD GaN-on-sapphire layers and associated quasi-vertical Schottky Barrier Diodes (SBDs). Samples’ GaN drift layers have globally a similar quality as examined by XRD, AFM Raman spectroscopy, C-V measurements and I-V characteristics. Some crystal defects in the GaN layer are identified by Raman spectroscopy and SEM, and their effect on the electrical characteristics of the diodes is assessed. Most of the SBDs have reverse current densities at −100 V that are comparable to that of some of the best vertical GaN-on-GaN SBDs, which can be correlated to drift layers’ doping homogeneity and dislocation density.