N/GaN Heterostructures Grown by Plasma-assisted Molecular Beam Epitaxy*

Polarization-induced high-mobility two-dimensional electron gases (2DEGs) at AlGaN/GaN heterostructures have been studied and used for ultrafast transistors. They offer an interesting platform to study quantum transport in the high electron effective mass regime. At room temperature, the mobility is dominated by optical phonon scattering, but at low temperatures, the mobility is determined by defect and imperfection based scattering mechanisms, and weakly by acoustic phonons. In this talk, we will present how gate control of the 2DEG density helps us identify the impact of dislocations on the mobility. We have used a range of samples in which the dislocation densities vary over 4 orders of magnitude. With the help of high magnetic field oscillation studies at low temperatures we extract the effect of dislocations on the low temperature scattering processes.