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This paper focuses on the detailed investigation of the structural and electronic properties of wurtzite AlN crystals doped by Li with and without oxygen with the first principles calculation. All the calculations have exhibited significant structural distortions. Compared with the monoclinic doping, the oxygen codoping has improved the structure deformation and lowered the formation energy of Li dopants. The calculated electronic density of states (DOS) reveals that all doping configurations still preserve semiconductor characteristics. The states around the valence band maximum cross the Fermi level, which implies p-type doping. The induced extra levels are extremely localized and flat in Li-doped AlN while much more delocalized in oxygen codoped models. The mono-doping of Li is in general energetically unfavorable while the codoping improves the formation and makes the intercalation of Li more stable in AlN. According to the results, the codoping configuration of Li with O in AlN has provided a useful way of modifying the corresponding properties.

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., 6 pages, 6 figures