Doping studies of N- and P-type AlXGa1-XN grown by ECR assisted MBE

AlxGa1-xN films (x less than or equal to 0.60) were grown on c-plane sapphire and (0001) 6H-SiC substrates using ECR plasma assisted Molecular Beam Epitaxy. Evidence of long range ordering in the investigated AlxGa1-xN films is presented. Without intentional dopants the films are semi-insulating with resistivities ranging from 10(3) to 10(5) Omega.cm. The films were doped n-type with Si and p-type with Mg. The carrier concentration in the Si doped films, as determined by Hall effect measurements, was between 10(16) to 10(19) cm(-3). At constant Si cell temperature, the carrier concentration was found to be reduced with AlN mole fraction, consistent with the observation that the donor ionization energy increases with Al content. Correspondingly, the electron mobility decreases with Al concentration, a result attributed to alloy scattering. The Mg doped films were found to exhibit p-type conductivity by thermoelectric power measurements with resistivities varying from 3 to 30 Omega-cm.