Modeling of 2DEG and Surface Barrier Height in ZnO-Based Heterostructures Using Surface States

It is well known that a two-dimensional electron gas (2DEG) exists at the MgZnO/ZnO interface. Both the formation mechanism and the origin of this 2DEG is of immense interest. The origin has been attributed to the polarization charge present coupled with the donor-like surface states on the MgZnO surface. In this paper, a physics-based model is described to explain the 2DEG as well as the bare surface barrier height by considering the low density surface donor states distributed over a range of energies below a particular donor energy level. The model shows good agreement with the reported experimental results. The model for the 2DEG in a MgZnO/CdZnO heterostructure is also analyzed.