Semipolar (11–22) AlN Films Grown by Hydride Vapor Phase Epitaxy for Schottky Barrier Diodes

Abstract

High-quality semipolar (11−22) AlN films with a thickness of 8.4 μm are grown on m-plane sapphire by high-temperature hydride vapor phase epitaxy (HVPE). The full widths at half-maximum (FWHMs) of X-ray rocking curves (XRCs) for such films are as small as 641″ and 346″ along [11−23] AlN and [1−100] AlN , respectively. Ohmic contacts with a specific contact resistance of 0.792 Ω•cm 2 are achieved on the unintentionally doped (11−22) AlN films by depositing a Ti/Al/Ni/ Au metal stack, combined with high-temperature rapid annealing at 950 °C. Based on the good crystal quality and ohmic contacts, lateral Schottky barrier diodes (SBDs) are fabricated on the semipolar AlN film. The Ni/Au-AlN SBDs exhibit an ideality factor n of 6.5 and an effective Schottky barrier height (SBH) of 1.12 eV at room temperature. At high temperatures, the ideality factor n falls, while the effective SBH grows, indicating lateral nonuniformities at the metal/semiconductor contact, which can be adequately explained by an inhomogeneous model. Moreover, the large band gap of AlN enables the manufactured SBDs to operate reliably even at a temperature of 450 K.