Ab-Initio computations of electronic and transport properties of wurtzite aluminum nitride

Abstract

We report findings from several ab-initio, self-consistent calculations of electronic and transport properties of wurtzite aluminum nitride. Our calculations utilized a local density approximation (LDA) potential and the linear combination of Gaussian orbitals (LCGO). Unlike some other density functional theory (DFT) calculations, we employed the Bagayoko, Zhao, and Williams' method, enhanced by Ekuma and Franklin (BZW-EF). The BZW-EF method verifiably leads to the minima of the occupied energies; these minima, the low laying unoccupied energies, and related wave functions provide the most variationally and physically valid density functional theory (DFT) description of the ground states of materials under study. With multiple oxidation states of Al (Al$^{3+}$ to Al) and the availability of N$^{3-}$ to N, the BZW-EF method required several sets of self-consistent calculations with different ionic species as input. The binding energy for (Al$^{+3}$ & N$^{3-}$) as input was 1.5 eV larger in magnitude than those for other input choices; the results discussed here are those from the calculation that led to the absolute minima of the occupied energies with this input. Our calculated, direct band gap for w-AlN, at the $\Gamma$ point, is 6.28 eV, in excellent agreement with the 6.28 eV experimental value at 5 K. We discuss the bands, total and partial densities of states, and calculated, effective masses.