Drain-Bias-Dependent Study of Reverse Gate-Leakage Current in AlGaN/GaN HFETs

Reverse gate-leakage of the AlGaN/GaN heterostructure field-effect transistors (HFETs) is studied at different values of drain-source voltage ( {V}_{\text {DS}} ), ranging from 0 to 10 V. Throughout the investigated range of {V}_{\text {DS}} , the reported analysis confirms the applicability of the Fowler-Nordheim (FN) tunneling as the dominant contributor to the gate-leakage for reverse gate biases until the onset of the threshold voltage. Device simulations were performed using Comsol Multiphysics to estimate the electric field ( E\,\, ) across the polar III-nitride barrier layer at different positions along the gate length. We observe that the FN tunneling takes place predominantly corresponding to the average electric field observed to be close to {E} at the center of the gate for lower values of {V}_{\text {DS}} , whereas at larger values of {V}_{\text {DS}} , FN tunneling corresponding to {E} only at the drain edge of the gate seems poised to deliver the gate-leakage current. In formulating the FN tunneling, the value of the electron effective mass is selected consistently within an acceptable range for analyzing gate-leakage. Investigating the applicability of FN tunneling in explaining the reverse gate-leakage current of AlGaN/GaN HFETs for the aforementioned values of gate to source voltage ( {V}_{\text {GS}} ) not just at zero {V}_{\text {DS}} , but across a range of {V}_{\text {DS}} values, seems to offer a more convincing argument for the hypothesis on tunneling through small leakage zones.