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.