Performance enhancement of AlGaN/GaN metal-oxide-semiconductor heterojunction field-effect transistor (MOSHFET) with atomic layer deposition (ALD) of high-k HfAlO gate dielectric layer

AlGaN/GaN heterojunction field effect transistors (HFET) are promising candidates for both power and RF applications due to their superior material properties. High-speed switching and reduction in power losses can be achieved by the use of the two-dimensional electron gas (2DEG) that forms between AlGaN barrier and GaN layer. However, a conventional HFET device with a Schottky gate suffers from high gate leakage current which in turn limits device performance. The incorporation of a gate dielectric layer between the Schottky gate and AlGaN barrier can suppress the gate leakage current but the electrical characteristics are subjected to dielectric quality caused by various deposition method. ALD deposition can provide several advantages such as low temperature processing, conformal deposition, and precise thickness control. By using ALD it is possible to deposit damage free dielectrics on AlGaN/GaN layer with low defect density resulting in the performance enhancement of the device. In this work, we investigate the electrical properties of a MOSHFET with ALD HfAlO gate dielectric and compare to the conventional HFET device.