GaN based high mobility electron transistors with regrown ohmic contacts

• Main Author: Weng, Don Letian
• Other Authors: Radhakrishnan K
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2024
• Subjects: Engineering
• Online Access: https://hdl.handle.net/10356/176547
• Institution: Nanyang Technological University

Gallium Nitride (GaN) based high mobility electron transistors (HEMT) has been heavily researched in recent times for its superior capabilities compared to Silicon and that there are still many untapped potentials behind it. To achieve devices with superior performance, good ohmic contacts with low resistivity are crucial. In this work, ohmic contacts are regrown using molecular beam epitaxy (MBE) to achieve an accurate thickness of the layers to obtain ohmic contacts with low resistivity. The doping of the GaN epilayer is carried out with Si and Ge and various measurements are carried out and compared against one another. Using AFM, Hall effect measurement and TLM measurements, a low contact resistance of 0.0953 Ω-mm was obtained for Ge-doped GaN and 0.1768 Ω-mm for Si-doped GaN. It is evident that germanium as a dopant is superior to silicon for doping of the GaN layer as it can dope GaN heavily compared to silicon and produce sheet resistance and contact resistances that are at least two times lower than that of silicon.