Charge based compact model for fin-shaped GaN HEMTs

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Name of the Speaker: Sruthi M. P (EE17D413)
Guide: Dr. Anjan Chakravorty
Venue/Online meeting link:
Date/Time: 16th March 2023, 5pm

Gallium nitride (GaN) is becoming a mainstream semiconductor for power and radio-frequency applications. Due to the superior material properties of GaN and the intrinsic advantages of the high electron mobility transistor (HEMT) structure, there has been an increased demand for GaN based HEMTs. Conventional GaN HEMTs are depletion mode or normally-ON devices. On the other hand, high performance normally-OFF GaN HEMTs eliminate the requirement of negative supply voltage and makes the circuit configurations simple. A gate electrode surrounding the channel can provide enhanced control over the electrons in the two-dimensional electron gas (2-DEG) resulting in a shift of threshold voltage towards the positive direction. Recently, fin-shaped HEMT (Fin-HEMT) structures have been introduced to use this advantage. They can realize superior gate controllability, and enhancement-mode operation with a higher current ON/OFF ratio as compared with the planar counterparts. To facilitate the use of these transistors for circuit design, robust compact models that accurately capture the behaviour of the device are needed.

In this talk, a charge based compact model for drain current in Fin-HEMTs will be presented. The model considers the effects of both the top and side gates on the charge densities inside the device through modified gate capacitance formulations. First, a closed form expression for 2-DEG density in Fin-HEMTs will be discussed. The total drain current which is modeled as the sum of 2-DEG and double-gate field effect transistor (FET) currents will be elaborated subsequently. A special feature of the model is that it can be used for different fin configurations by changing the corresponding equivalent circuits. Finally, the model validation with experimental data will be presented.