Impact of gate dielectric thickness on the electrical properties of AlGaN/GaN MISHFETs on Si(111) substrate

Abstract

AbstractWe report on the fabrication and characterization of AlGaN/GaN metal–insulator–semiconductor heterostructure field effect transistors (MISHFETs) using HfO2 and Al2O3 as gate dielectric, deposited by atomic layer deposition (ALD). Improved device performance has been observed for all MISHFET devices as compared to the reference HFET. The additional dielectric layer underneath the gate metallization leads to a significant decrease of gate leakage currents and thus prevents device degradation and losses. Furthermore, the 2DEG sheet carrier concentration increases depending on the k‐value of the oxide as well as the oxide thickness. The thin (3–9 nm) dielectric layer is serving simultaneously as surface passivation, mitigating dc‐to‐rf dispersion. However, less has been reported about the impact of gate insulator thickness on the electrical performance, in particular in terms of dc‐to‐rf dispersion. In this paper, full recovery of dc drain current is demonstrated with a MISHFET with 9 nm Al2O3 oxide thickness.