Improved interface state density by low temperature epitaxy grown AlN for AlGaN/GaN metal-insulator-semiconductor diodes

Abstract

AlGaN/GaN metal-insulator-semiconductor (MIS) diodes were fabricated using low temperature epitaxy (LTE) grown AlN at 200 °C, a technique combining both physical vapor deposition and chemical vapor deposition. The interface trap characteristics of the MIS-diodes were investigated using the frequency dependent parallel conductance method. Two distinct interface trapping regions were observed, where the fast interface traps had an estimated density (Dit) as low as 6.7 × 1011 cm−2 eV−1 while the slow interface traps Dit were as low as 6.8 × 1011 cm−2 eV−1. About 3.8 × improvement in Dit was achieved compared to our previous work by optimization of the LTE deposition conditions. The fast traps are located within the energy interval of 0.24–0.30 eV below the conduction band while the slow traps are located 0.44–0.56 eV below the conduction band. The observed fast traps were associated with the AlGaN/GaN interface, while the observed slow traps may have formed at AlN/GaN interface during the deposition of AlN by LTE.