GaN‐based high‐frequency devices and circuits: A Fraunhofer perspective

Abstract We present the current status of our technology for GaN‐based HEMTs and MMICs as well as results ranging from the L‐band up to the W‐band. Epitaxial growth is carried out on 4H‐SiC(0001) substrates by both MOCVD and MBE. Processing is done using standard III–V equipment including both frontside and backside processing. For L‐band power bars we arrive at output powers, efficiencies and gains beyond 100 W, 60% and 17 dB, all measured under cw conditions at 50 V drain bias. The X‐band MMICs are characterized by a high efficiency above 40% for two‐stage amplifiers. Towards mm‐wave applications we have fabricated HEMTs with transit frequencies above 100 GHz and W‐band MMICs delivering 0.5 W/mm at 94 GHz with 7% PAE. First quaternary InAlGaN barriers show promising results for this new materials system. Reliability tests return a very good long‐term stability of our devices even at an elevated channel temperature of 200 °C with an extrapolated lifetime of 5 × 10⁵. Initial space capability tests including total ion dose radiation insensitivity, radiation displacement damage, hydrogen poisoning and single event effect are successfully passed.