Tungsten-Gated GaN/AlGaN p-FET With Imax > 120 mA/mm on GaN-on-Si

This letter demonstrates Tungsten (W)-gated
${p}$
-channel GaN/AlGaN heterostructure field effect transistors on a GaN-on-Si wafer grown by metal organic chemical vapor deposition (MOCVD). The choice of W as the gate metal over the more commonly used Mo induces larger turn-on voltage and lower gate leakage current. An annealing step at 500 °C in N
₂
ambient was introduced to heal the damage introduced during the gate recess step which resulted in lower channel resistance. Long-channel W-gated
${p}$
-FETs with
$L_{{\mathrm {SD}}}=5.5\,\, {\mu }\text{m}$
and
$L_{{\mathrm {G}}}=1.5\,\,{\mu }\text{m}$
exhibits an
$I_{{\mathrm {ON}}} \approx 25$
mA/mm,
$I_{{\mathrm {ON}}}/I_{{\mathrm {OFF}}}>10^{3}$
. A scaled transistor of dimensions
$L_{{\mathrm {SD}}}=1.2\,\,{\mu }\text{m}$
and
$L_{{\mathrm {G}}}=100$
nm demonstrates an
$I_{{\mathrm {ON}}} \approx 125$
mA/mm,
$I_{{\mathrm {ON}}}/I_{{\mathrm {OFF}}}\approx 10^{4}$
, and
$R_{{\mathrm {ON}}}=170\,\,{\Omega }\cdot {\mathrm {mm}}$
.