Thermal stability of sheet resistance in AlGaN/GaN 2DEG structure

An annealing study of an AlGaN/GaN two-dimensional electron gas structure was conducted in combination with precise AlGaN thickness measurements using reflectivity spectra. It is found that the sheet resistance increases when annealing is performed below the growth temperature, and the increase depends on the AlGaN thickness and crystal quality. One possible explanation for the increase is that Si donors in low-quality AlGaN layers are passivated or compensated from the top surfaces upon annealing.