Atomic layer deposition Al2O3-passivated AlGaN/GaN high-electron-mobility transistors on Si(111) towards reliable high-speed electronics

AlGaN/GaN HEMT, Si(111), high-speed electronics

Lee, Hsuan-Ping

关键词: AlGaN/GaN HEMT, Si(111), high-speed electronics;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/107848/LEE-DISSERTATION-2020.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

(Al)GaN-based transistors are the backbones of next-generation high power/frequency electronics. However, various challenges with this exciting technology still necessitate more comprehensive investigations. In particular, epitaxially growing high-quality (Al)GaN layers on foreign substrates, forming low-resistance ohmic contacts on (Al)GaN materials, properly passivating (Al)GaN surfaces, and reducing leakage currents are of great importance. In this dissertation, these challenges are individually addressed along with respective detailed studies.It is shown that a low GaN in-plane tensile strain allows a higher 2D electron gas mobility due to the alleviated interface roughness scattering. In addition, an ohmic contact specific resistance of 4 × 10-6 Ω–cm2 with Ti/Al/Ni/Au metal stacks has been achieved by three-step rapid thermal annealing. Furthermore, it is revealed that annealed, thin-Al2O3 dielectric is an effective (Al)GaN surface passivation alternative for minimizing passivation-associated parasitic capacitance, yet non-ideal for significantly suppressing gate leakage current in metal-insulator-semiconductor structures due to the governing trap-assisted tunneling carrier transport mechanism. A 3.5 µm Schottky-gate AlGaN/GaN HEMT with VT and gm of -0.87 V and 131.67 mS/mm, respectively, at VDS = 3.5 V has been demonstrated. The measured high Schottky gate leakage current and OFF-state drain current are believed to be responsible for the large subthreshold swing and low drain current on/off ratio. A passivation-last process followed by post-metallization annealing is then utilized, which largely reduces the reverse biased Schottky-gate leakage current and OFF-state drain current, leading to a low subthreshold swing of 84.75 mV/dec and a high drain current on/off ratio of 2.1 × 107. Together, the presented results add constructive inputs to the realization of reliable AlGaN/GaN HEMTs on Si(111) towards reliable high-speed electronics.