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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 Φ B = 0.82 eV, low turn-on voltage ∼0.56 V, leakage current density of J R < 5.5 × 10−6 Acm−2 at −100 V, breakdown voltage V BR < −200 V, and less interface state density (N SS < 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 Φ B and n is detected from I–V-T measurements. Similar traps at E C - 0.18 eV and E C - 0.56 are identified in the various SBDs from DLTFS, signifying that these traps are omnipresent defects in the epilayer. • Comprehensive characterizations are carried out for vertical GaN-on-GaN Schottky barrier diodes (SBDs). • Typical electrical characteristics of quasi-ideal vertical GaN-on-GaN SBDs are reported. • Various current transport mechanisms involved during forward and reverse characteristics of the SBD are identified. • The GaN active layer properties are evaluated by AFM, SIMS, micro-Raman spectroscopy, cathodoluminescence (CL). • Furthermore, traps in the GaN diodes are detected by deep level transient Fourier spectroscopy (DLTFS). [ABSTRACT FROM AUTHOR]