CC BY 4.0John, LaurenzLaurenzJohnTessmann, AxelAxelTessmannLeuther, ArnulfArnulfLeutherMerkle, ThomasThomasMerkleMaßler, HermannHermannMaßlerChartier, SébastienSébastienChartier2022-07-052022-07-052022https://publica.fraunhofer.de/handle/publica/41861110.24406/h-41861110.1109/LMWC.2022.316009310.24406/h-418611In this letter, we report on the development of highgain WR-1.5 amplifier circuits, utilizing a transferred-substrate InGaAs-on-insulator (InGaAs-OI) high-electron-mobility transistor (HEMT) technology on Si with 20-nm gate length. A six-stage and a nine-stage amplifier circuit are described, which are based on gain cells in cascode configuration. With more than 30 dB of measured gain in the frequency band of 660-700 GHz, the highest frequency of operation of transferred-substrate THz amplifiers is reported. These gain levels in excess of 30 dB, furthermore, correspond to the highest reported gain values and state-of-theart performance around the targeted 670-GHz frequency band.enAmplifiershigh-electron-mobility transistorHEMTInGaAs-on-insulator (InGaAs-OI)siliconTHzjournal article