Theoretical analysis of the mobility of two-dimensional electron gas in the quaternary AlxInyGa1-x-yN/GaN heterojunctions limited by the alloy composition fluctuation

We established the model of the electron mobility limited by the alloy composition fluctuation scattering in the quaternary AlxInyGa1-x-yN/GaN heterojunctions for the first time. The alloy composition fluctuation along the AlxInyGa1-x-yN/GaN heterointerface was considered and characterized by the lateral correlation length L, and the fluctuations of aluminum and indium mole fractions (Δx and Δy) independent to each other. The situation of alloy composition fluctuation is investigated in the following cases. Only x or y fluctuates, and both x and y fluctuate with equal/unequal amplitudes in the same/opposite direction. We find that the scattering with both x and y fluctuating in the same direction is the weakest, while x and y fluctuating in the opposite directions leads to the strongest scattering. This in nature stems from the disparity of the bandgap and polarization in AlInN, AlGaN and GaN. The effects of different parameters, such as x and y, Δx and Δy, L, and the thickness of AlxInyGa1-x-yN barrier layer d on the mobility are also studied. The model will in principle give a universal explanation to the effect of alloy composition fluctuation scattering on the carrier mobility in the GaN-based heterostructures with ternary or quaternary alloy barrier layers.