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Wide band-gap (WBG) materials such as GaN and SiC are playing an increasingly important role in modern high-frequency and high-power electronic technologies. As advances in bulk growth continue to lower defect densities and improve crystalline quality, these semiconductors are also emerging as strong contenders for next-generation radiation detectors. Nevertheless, extensive optimisation and detailed characterisation are still needed before they can realistically compete with silicon in demanding radiation-intensive applications.
GaN, in particular, benefits from its large band gap (3.4 eV) and robust Ga–N bonding, which together indicate strong thermal stability and excellent resistance to radiation damage. Although GaN-based detector structures have been demonstrated, most rely on epitaxial GaN layers deposited on foreign substrates such as Si, SiC or sapphire. As a result, the behaviour and reliability of fully GaN-on-GaN devices in extreme environments are not yet comprehensively understood. Achieving wider use of these devices in harsh-radiation scenarios will require continued development and systematic characterisation.
In this work, Schottky diodes of varying geometries were fabricated on an n-type GaN bulk wafer with an n⁻ epilayer. Following metal rapid thermal annealing (500°C for 2 minutes), the devices were characterized via current–voltage (I–V) and capacitance–voltage (C–V) measurements, exhibiting typical Schottky behaviour with design-dependent variations. Despite exhibiting typical rectification, the devices show high leakage current, high series resistance and evident barrier inhomogeneity.
A comprehensive temperature-dependent (233K to 573K) analysis of the forward-bias characteristics was performed to assess and improve their suitability as radiation detectors. This has allowed deeper insight into the underlying physical mechanisms driving the observed trends. In this work, barrier inhomogeneity was identified via Gaussian distributions, resistance corrections, and identification of typical inhomogeneous barrier trends. Its dependence on device perimeter and area was subsequently investigated. In addition, the prevalent current transport mechanisms have been studied, suggesting thermionic field emission (TFE) seen at low temperatures and bias voltages and thermionic emission (TE) as the dominant mechanism. Ultimately, elucidating the next steps in fabrication towards functional radiation detectors.