An Improved Compact Model of T-Gate HEMT Based on Effective Gate Length

Advanced SPICE Model for high electron mobility transistor (ASM-HEMT) is one of the industry standard models for GaN-based high electron mobility transistors (HEMTs), in which there still lack analytical models for the distribution of the physical properties inside the device, especially a model for the distribution of the transverse electric field (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${E}_{\text {X}}$ </tex-math></inline-formula>) and carrier concentration (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${n}_{\text {S}}$ </tex-math></inline-formula>) that can be linked to the drain current (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I}_{\text {DS}}$ </tex-math></inline-formula>) and gate charge (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Q}_{\text {G}}$ </tex-math></inline-formula>). Besides, the modeling of operations in the saturation region in ASM-HEMT is dependent on empirical parameters without physical significance. In this work: 1) effective gate length (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${L}_{\text {G,eff}}$ </tex-math></inline-formula>) as a core parameter for saturation region modeling is calculated to capture the velocity saturation occurring in HEMTs; 2) distribution of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${E}_{\text {X}}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${n}_{\text {S}}$ </tex-math></inline-formula> varying with gate and drain biases in the linear and saturation regions is modeled; 3) a field plate (FP) aware T-gate HEMT model is developed to capture the reduction of the peak electric field and the additional parasitic effect caused by the FP. The model is verified by characterizing the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I}_{\text {DS}}$ </tex-math></inline-formula> and Miller capacitance (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${C}_{\text {GD}}$ </tex-math></inline-formula>) of the fabricated T-gate HEMTs, with RMSE lower than 7.5%, indicating a high degree of agreement.