Impurity band formation in doped AlN: A Green’s function approach

Using a Green’s function approach, we present a thorough theoretical analysis of impurity band formation in wurtzite aluminum nitride (AlN) for the case of uncompensated n-type doping. A multiple-scattering approach is applied to the calculation of self-energies, correct to first order in the dopant concentration, from which electronic dispersion may be extracted. The unperturbed band structure of AlN is calculated according to a 4×4k·p Hamiltonian, which captures the anisotropy of all bands. Our findings demonstrate the influence of dopant concentration on impurity band dispersion, bandwidth, densities of state, and effective masses for n-type AlN. Without appreciable anisotropy in the conduction band, the observed donor band dispersion in AlN is itself nearly isotropic. To improve the design and functionality of AlN-based electrical and optoelectronic devices, this work offers a qualitative, conceptual foundation for further study of electrical contacting to n-type material and impurity band conduction.