A stack of TiN/Ru was employed as the Schottky gate metal for a nitrogen-polar deep-recess GaN high electron mobility transistor (HEMT) on a sapphire substrate. TiN/Ru Schottky diodes fabricated on the same HEMT epitaxy demonstrated a 6

$\times$

reduction in reverse-bias leakage current compared to Ru-only counterparts. The addition of TiN also resulted in a clear improvement in breakdown voltage for scaled N-polar Schottky gate HEMTs, as measured by the drain-current injection method (DCI). TiN HEMTs exhibited a peak

$\textit{g}_{\text{\textit{m},dc}}$

of 843 mS/mm. A HEMT with a gate length (

$L_{\text{\textit{g}}}$

) of 50 nm demonstrated a peak

$\textit{g}_{\text{\textit{m},RF}}$

of 1028 mS/mm, peak

$f_{t}$

of 193 GHz, and peak

$f_{\max}$

of 362 GHz. Load–pull was measured at 94 GHz with a

$V_{\text{DS}}$

of 12 V and

$I_{\text{DS}}$

of 250 mA/mm. The TiN HEMT demonstrated a power added efficiency (PAE) of 53.4%—a record for N-polar GaN at

$W$

-band. The associated output power density was 3.7 W/mm, and the linear power gain (G

$_{\text{\textit{p}}}$

) was an exceptional 10.2 dB.

	Year	Citations

About