N-Polar GaN MISHEMT With Bias-Insensitive Linearity at 30 GHz

A varying channel thickness was induced on nitrogen-polar GaN through undulations associated with step-bunching on a miscut vicinal substrate. Subsequently, the fabricated deep-recess metal insulator semiconductor high electron mobility transistors (MISHEMT) exhibited a varying threshold voltage along the gate width. A low third-order transconductance (
${g}_{m3}$
) was observed, indicating a third-order output-referred intercept point over dc power (OIP3/PDC) which was bias-insensitive. Two-tone 30-GHz load–pull demonstrated a peak OIP3/PDC of 11.95 dB, which remained above 8 dB for two
$\Delta V_{\text {GS}}$
windows of 0.5 and 0.3 V at
$V_{\mathbf {DS}}$
of 7 V. Single-tone 94-GHz load–pull measured at
$V_{\text {DS}}$
of 12 V showed a peak output power density of 4.9 W/mm and an associated PAE of 33.9%.