Advancements to physics-based modelling of gallium nitride high-electron mobility transistors

Gallium nitride (GaN) high-electron mobility transistors (HEMTs) have been a topic of rigorous research over the past several decades due to the promising theoretical properties of the GaN-based material system, where such properties include high carrier mobility, high breakdown voltages, high saturation velocity etc. Throughout the development of the GaN-based material system, it has been of an equal importance that a robust and accurate compact model for GaN HEMTs is standardised in order to allow for the translation of such devices into real world circuit applications. During recent times, the industry has seen the standardisation of the Advanced Spice Model for GaN HEMTs, ASM-HEMT, which is a physics-based compact model derived from the core formulations of the surface potential. As the GaN-based material system is still within its infancy, the importance of a robust and accurate physics-based compact model allows for meaningful insights into the development of device fabrication where the associated parameters pertain to the intrinsic device physics. This provides designers, at both the device and circuit level, with a more meaningful model card where the true performance of a design can be analysed at the fundamental level. As the GaNbased material system progresses, it is of the utmost importance that the ASM-HEMT model advances alongside with it. Naturally, in order for the ASM-HEMT model to be accepted as an industry standard model, it is already considered as an extremely robust and accurate compact model. However, due to the progressive nature of the GaN-based material system, advanced devices have been seen to exhibit characteristics that demand to be accounted for. The research efforts presented in this thesis serve as proposal methodologies to account for such characteristics which adhere to the physics-based nature of the ASM-HEMT model.