6-Inch GaN-on-Si Gold-Free Fabrication Technolgies for Monolithic Microwave Integrated Circuits (MMICs)

We have fabricated GaN HEMTs with gate lengths of 0.5 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mu \mathrm{m}$</tex> and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.25 \mu \mathrm{m}$</tex> on 6-inch silicon-based GaN substrates using a gold-free process. The <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.5 \mu \mathrm{m}$</tex> devices exhibit a maximum drain current density (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{I}_{\text{dmax}}$</tex>) of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$680 \text{mA} / \text{mm}$</tex>, a peak transconductance (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathrm{G}_{{\max}}$</tex>) of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$230 \text{mS} / \text{mm}$</tex>, and small-signal characteristics with a cutoff frequency (fT) and maximum oscillation frequency (fmax) of 19 GHz and 28 GHz, respectively. Continuous wave (CW) loadpull measurements at 3.6 GHz demonstrate an output power density of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$3.1 \mathrm{W} / \text{mm}$</tex>, a peak power added efficiency (PAE) of 43.5 %, and a linear gain of 20 dB. The <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.25 \mu \mathrm{m}$</tex> devices show a maximum drain current density (Imax) of 979 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{mA} / \text{mm}$</tex>, a peak transconductance (Gmax) of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$286 \text{mS} / \text{mm}$</tex>, and small-signal characteristics with a cutoff frequency (fT) and maximum oscillation frequency (fmax) of 34 GHz and 50 GHz, respectively. CW loadpull measurements at 10 GHz yield an output power density of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$2.71 \mathrm{W} / \text{mm}$</tex>, a peak power added efficiency (PAE) of 44.5 %, and a linear gain of 12 dB. The low and uniform ohmic contact resistance (Rc) of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.2-0.3 \Omega \cdot \text{mm}$</tex> across the wafer indicates the potential for high-performance and cost-effective 6-inch GaN with silicon CMOS compatibility for RF applications.