Growth and characterization of nitrogen-polar AlGaN/AlN and demonstration of field effect transistor

Abstract

This study proposes a nitrogen-polar (N-polar) Al x Ga1−x N/Al0.9Ga0.1N/AlN structure that can generate a large amount of two-dimensional electron gas to enhance the device development of samples. Additionally, we have analyzed the critical thickness of N-polar AlGaN/AlN based on the theoretical calculations of three different values of film thickness. The metalorganic vapor-phase epitaxy method is used to grow N-polar Al x Ga1−x N/Al0.9Ga0.1N/AlN on sapphire substrates. The substrates with a misorientation angle of 2° along the m-axis and a-axis directions are selected to determine the effect of the off-cut angle on sample flatness and current–voltage characteristics. Furthermore, we determine the effect of Al contents on N-polar Al x Ga1−x N/Al0.9Ga0.1N/AlN under the optimum growth conditions of the growth thickness of the top layer of AlGaN and sapphire substrate. The results indicate that the current throughput increases with a decrease in Al content. Lastly, we have fabricated the N-polar AlGaN/AlN heterostructure field effect transistor (FET) to demonstrate the static FET characteristics.