Barrier Inhomogeneity of Schottky Diode on Nonpolar AlN Grown by Physical Vapor Transport

An aluminum nitride (AlN) Schottky barrier diode (SBD) was fabricated on a nonpolar AlN crystal grown on tungsten substrate by physical vapor transport. The Ni/Au–AlN SBD features a low ideality factor ${n}$ of 3.3 and an effective Schottky barrier height (SBH) of 1.05 eV at room temperature. The ideality factor ${n}$ decreases and the effective SBH increases at high temperatures. The temperature dependences of ${n}$ and SBH were explained using an inhomogeneous model. A mean SBH of 2.105 eV was obtained for the Ni–AlN Schottky junction from the inhomogeneity analysis of the current–voltage characteristics. An equation in which the parameters have explicit physical meanings in thermionic emission theory is proposed to describe the current–voltage characteristics of inhomogeneous SBDs