Critical parameters for the presence of a 2DEG in GaN/AlxGa1−xN heterostructures

In this computational study, the influence of GaN/AlxGa1−xN layer stack parameters, such as surface potential, aluminum mole fraction, and background donor concentration, on the two-dimensional electron gas (2DEG) density in a heterostructure is verified. At a fixed Al mole fraction, the surface potential was identified to have the largest impact on the 2DEG density. The combination of a small aluminum mole fraction (x < 0.12) and large surface potential results in the absence of a 2DEG in the investigated heterostructures, while for a small surface potential value, a 2DEG will be present. For a large aluminum mole fraction (x ≥ 0.25), a 2DEG is always present, independent of the surface potential value. In the case of an intermediate aluminum mole fraction, the background donor level is one key parameter strongly influencing the 2DEG density.