Electrical properties of Nb/Au Schottky contacts on p-GaN:Mg enabling high-performance rectification and trap-depleted barrier landscape

Abstract

This Letter introduces a novel Nb/Au metallic system toward the realization of high-performance Schottky contacts on p-type GaN:Mg. In particular, the influence of depositing a thin niobium layer on the p-GaN surface was investigated toward the realization of low reverse leakage current, a close-to-ideal ideality factor (n), a high ON/OFF ratio, and a minimal interface state density (Dit). The fabricated Nb/p-GaN Schottky barrier diodes exhibit an ON/OFF current ratio of 2 × 106, an ideality factor of 1.4, and a Schottky barrier height (ΦB) of 1.0 eV extracted from forward current–voltage (I–V) measurements. Despite the moderate barrier height, the reverse leakage current density is strongly suppressed, reaching 1.5 × 10−6 A/cm2 at −2.5 V, indicating that carrier transport is governed by the ensemble-averaged barrier rather than localized low-barrier patches. Capacitance–frequency (C–F) and conductance–frequency (G–F) measurements reveal Dit of ∼1012–1013 cm−2 eV−1, such that trap-assisted processes do not dominate carrier transport. Temperature-dependent electrical measurements confirm thermionic-emission (TE) dominated conduction over a wide bias and temperature range, with negligible barrier degradation. Unlike conventional Schottky metals on p-GaN, where reverse transport is frequently governed by barrier inhomogeneity and field-assisted leakage, Nb yields an electrically stable interface with suppressed trap activity without post-metallization annealing. The central novelty of this work lies in demonstrating that Nb enhances p-GaN Schottky performance by stabilizing the barrier landscape through trap depletion and spatial homogenization rather than barrier height maximization. These findings establish Nb as a performance-optimized Schottky metal for p-GaN rectifiers and gate interfaces.