Analytical Model on the Threshold Voltage of p-Channel Heterostructure Field-Effect Transistors on a GaN-Based Complementary Circuit Platform

To realize the complementary circuit on the GaN-on-Si platform, an investigation of p-channel heterostructure field-effect transistors (p-HFETs) is necessary. In this study, an analytical model for the estimation of the threshold voltage (
${V}_{\text {TH}}$
) for GaN-based p-HFETs was developed. In this model, the impact of polarization charges at different interfaces, the influence of interface charges at oxide/GaN interface, as well as the out-diffusion effect of Mg dopant in the p-GaN layer were all taken into consideration for systematic exploration. Herein, GaN-based p-HFETs were fabricated to verify the relationship between the
${V}_{\text {TH}}$
and the thickness of the GaN channel layer by using the proposed model. The
${V}_{\text {TH}}$
model was further confirmed through TCAD simulations. The influences of the thickness of oxide layer, Mg doping concentration in p-GaN layer, and the Al mole fraction of Al
_x
Ga
$_{{1}-{x}}\text{N}$
layer on
${V}_{\text {TH}}$
were also discussed in detail. The model serves as more accurate guidance for the optimization of such p-HFETs design and complementary circuits.