High Gain 220 - 275 GHz Amplifier MMICs Based on Metamorphic 20 nm InGaAs MOSFET Technology

Compact high gain 220 to 275 GHz millimeter wave monolithic integrated circuit (MMIC) amplifiers have been developed, based on a metamorphic 20 nm gate length InGaAs metal-oxide-semiconductor field-effect transistor (MOSFET) technology. Therefore, an Al2O3/HfO2layer stack was deposited as a gate dielectric directly on top of an $\mathbf{In}_{0.8}\mathbf{Ga}_{0.2}\mathbf{As}$ channel by atomic layer deposition. The gate layout was optimized for millimeter wave and submillimeter wave integrated circuit applications using T-gates and wet chemical recess etching to minimize the parasitic gate capacitances. For a $2\times 10\ \mu \text{m}$ gate width transistor, a transit frequency $f_{\text{T}}$ of 275 GHz and a record maximum oscillation frequency $f_{max}$ of 640 GHz was extrapolated. A realized three-stage cascode amplifier circuit demonstrated a maximum gain of 21 dB at 263 GHz and a small-signal gain of more than 18 dB between 222 and 274 GHz. The total chip size of the millimeter wave amplifier MMIC was only $0.5\times 1.2\ \mathbf{mm}^{2}$.