Characteristics of GaN MIS-HEMT with ZrO2/HfO2 Superlattice Gate Dielectric Layer

This study investigated GaN metal-insulator-semiconductor high-electron-mobility transistors (MISHEMTs) with ZrO2/HfO2 superlattice (HZO-SL) gate dielectric, enabling improved gate quality and ferroelectric functionality. The unannealed HZO-SL provides low leakage and excellent interface control, while post-annealed HZO-SL exhibits ferroelectric polarization-driven hysteresis in the ID-VG characteristics. Devices with unannealed HZO-SL gate dielectric and SiN passivation layer in the source/drain access regions, exhibited I-V characteristics with negligible hysteresis and reduced gate leakage current. The off-state drain current of HZO-SL gated MISHEMT is approximately three orders of magnitude lower than Schottky gate HEMTs and one order of magnitude lower than HfO2 gated MISHEMT due to suppressed gate leakage. Moreover, a low subthreshold slope of 72 mV/dec indicated an outstanding interfacial quality. The MISHEMT also demonstrated excellent dynamic Ron behavior, achieving a dynamic-to-static Ron ratio of 1.16 (@VD=100 V). Additionally, ferroelectric-gate MISHEMTs were fabricated by employing a 500-600℃ annealed HZO-SL layer as both gate dielectric and surface passivation layer. These devices exhibited counter-clockwise I-V hysteresis, with memory windows (MW) ranging from 0.6 to 1.1 V, depending on the annealing temperature. The introduction of programmable hysteresis characteristics into GaN MISHEMTs offers a pathway for development of multifunctional GaN-based devices.