Implementation of High-Power-Density <inline-formula> <tex-math notation="LaTeX">$X$ </tex-math></inline-formula>-Band AlGaN/GaN High Electron Mobility Transistors in a Millimeter-Wave Monolithic Microwave Integrated Circuit Process

Abstract

A GaN high electron mobility transistor monolithic microwave integrated circuit (MMIC) designer typically has to choose a device design either for high-gain millimeter-wave operation with a short gate length, or for high-power-density <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$X$ </tex-math></inline-formula> -band operation with a much larger gate/field-plate structure. We provide the designer the option of incorporating two different devices by implementing a 0.14- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> gate length GaN MMIC process capable of high-efficiency Ka-band operation while simultaneously achieving high power density in the same process flow. The key process enabler simply uses the capacitor top plate in the MMIC process as a field plate on the passivation layer. On two separate devices on the same chip using the same MMIC process flow, we demonstrate 7.7 W/mm at 35 GHz and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{\mathbf {DS}}=30$ </tex-math></inline-formula> V on a standard <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4 \,\, \times \,\, 65$ </tex-math></inline-formula> - <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> T-gated FET and then 12.5 W/mm at 10 GHz and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{\mathbf {DS}}=60$ </tex-math></inline-formula> V on a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4 \,\, \times \,\, 75$ </tex-math></inline-formula> - <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> T-gated FET by adding a field plate. These are the highest reported power densities achieved simultaneously at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$X$ </tex-math></inline-formula> -band and Ka-band in a single wideband GaN MMIC process.