Tungsten-Gated GaN/AlGaN <i>p</i>-FET With I_max &gt; 120 mA/mm on GaN-on-Si

Abstract

This letter demonstrates Tungsten (W)-gated <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${p}$ </tex-math></inline-formula> -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 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ambient was introduced to heal the damage introduced during the gate recess step which resulted in lower channel resistance. Long-channel W-gated <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${p}$ </tex-math></inline-formula> -FETs with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$L_{{\mathrm {SD}}}=5.5\,\, {\mu }\text{m}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$L_{{\mathrm {G}}}=1.5\,\,{\mu }\text{m}$ </tex-math></inline-formula> exhibits an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$I_{{\mathrm {ON}}} \approx 25$ </tex-math></inline-formula> mA/mm, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$I_{{\mathrm {ON}}}/I_{{\mathrm {OFF}}}&gt;10^{3}$ </tex-math></inline-formula> . A scaled transistor of dimensions <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$L_{{\mathrm {SD}}}=1.2\,\,{\mu }\text{m}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$L_{{\mathrm {G}}}=100$ </tex-math></inline-formula> nm demonstrates an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$I_{{\mathrm {ON}}} \approx 125$ </tex-math></inline-formula> mA/mm, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$I_{{\mathrm {ON}}}/I_{{\mathrm {OFF}}}\approx 10^{4}$ </tex-math></inline-formula> , and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$R_{{\mathrm {ON}}}=170\,\,{\Omega }\cdot {\mathrm {mm}}$ </tex-math></inline-formula> .