Effect of growth conditions on the conductivity of Mg doped p-type GaN by Molecular Beam Epitaxy

The performance of III-V nitride heterostructure bipolar transistors has been limited by highly resistive p-type layers, in addition to difficulties associated with a precise p-n junction placement at the emitter-base heterojunction due to the Mg-memory effect during growth by Metal-Organic Chemical Vapor Deposition. The problem of precise p-n heterojunction placement can be solved by Molecular Beam Epitaxy growth. To investigate this possibility, in this work, we present a comprehensive study of the effect of III/N ratio, growth temperature, and Mg doping on the resistivity of Mg doped GaN layers grown by Molecular Beam Epitaxy. N(2)-rich growth conditions are found to lead to a temperature-independent low hole mobility, as opposed to Ga-rich growth conditions that lead to higher hole mobilities that vary with temperature. In addition, the growth temperature, Ga flux, and Mg flux windows leading to the highest p-type conductivity are identified.