Formation of a quasi-two-dimensional electron gas in GaN/Al x Ga 1x N heterostructures with diffuse interfaces

Calculations of the electronic energy levels and the distribution of the quasi-two-dimensional electron gas ͑Q2DEG͒ at the GaN/Al x Ga 1Ϫx N interface that take into account the graded nature of the interface are presented in this article. Mapping of the interface using scanning transmission electron microscopy annular dark-field imaging, the changes in the N K-edge and the integrated intensity of the Al L 2,3-edge revealed that the interface can be up to 20 Å wide. Self-consistent calculations in the local density approximation estimate the sensitivity of the Q2DEG formed at the interface to various parameters, including the width of the interface, the concentration of bound charge, ambient temperature, and the geometrical sizes of the structure.