Comprehensive characterization of vertical GaN-on-GaN Schottky barrier diodes

Abstract

This paper reports comprehensive characterization of vertical GaN-on-GaN Schottky barrier diodes (SBDs) fabricated on free-standing GaN substrates. The GaN active layer properties are evaluated by atomic force microscopy (AFM), secondary-ion mass spectrometry (SIMS), micro-Raman spectroscopy, cathodoluminescence (CL), and deep-level transient Fourier spectroscopy (DLTFS). The GaN SBDs exhibit near-unity ideality factor (n = 1.1), promising Schottky barrier height (SBH) of ΦB = 0.82 eV, low turn-on voltage ∼0.56 V, leakage current density of JR < 5.5 × 10−6 Acm−2 at −100 V, breakdown voltage VBR < −200 V, and less interface state density (NSS < 5 × 1012 eV−1 cm−2) at the Ni/GaN Schottky contact. The forward and reverse current transport mechanisms of the SBD are identified by fitting analysis of measured J-V. Weak temperature dependence of ΦB and n is detected from I–V-T measurements. Similar traps at EC - 0.18 eV and EC - 0.56 are identified in the various SBDs from DLTFS, signifying that these traps are omnipresent defects in the epilayer.