Regrown ohmic contact to GaN-based high electron mobility transistors

GaN-based High Electron Mobility Transistors have been of great interest for applications in high temperature, high frequency, high speed, and high power devices. GaN-based HEMTs have properties like wide bandgap, high saturation, and high critical breakdown field, making them favourable for further development and investigation. To realize high-performance AlGaN/GaN HEMT devices, good ohmic contacts with low resistivity are critical. In this study, ohmic contacts are regrown with the use of molecular beam epitaxy (MBE) to obtain controlled and precise thickness layers to realize the goal of a low ohmic contact. Using transmission line measurements, the contact resistance of regrown ohmic contacts are estimated and compared with alloyed ohmic contacts. A low contact resistance of 0.106 Ω-mm for AlGaN/GaN HEMT and 0.117 Ω-mm for AlGaN/AlN/GaN HEMT were obtained in this research thesis. Moreover, theoretical estimation of components of ohmic contacts were calculated, and is used to extract the resistance (R2) of current traveling path in the regrown ohmic contact. A wide variation in the R2 suggested that the theoretical estimation of R1 and R3 may not be accurate and needs further modification.Bachelor of Engineering (Electrical and Electronic Engineering