AlGaN/GaN MIS-HEMT using NbAlO dielectric layer grown by atomic layer deposition

We present an AlGaN/GaN metal—insulator—semiconductor high electron mobility transistor (MIS-HEMT) with an NbAlO high-k dielectric deposited by atomic layer deposition (ALD). Surface morphology of samples are observed by atomic force microscopy (AFM), indicating that the ALD NbAlO has an excellent-property surface. Moreover, the sharp transition from depletion to accumulation in capacitance—voltage (C—V)curse of MIS-HEMT demonstrates the high quality bulk and interface properties of NbAlO on AlGaN. The fabricated MIS-HEMT with a gate length of 0.5 μ m exhibits a maximum drain current of 960 mA/mm, and the reverse gate leakage current is almost 3 orders of magnitude lower than that of reference HEMT. Based on the improved direct-current operation, the NbAlO can be considered to be a potential gate oxide comparable to other dielectric insulators.