Development of AlGaN/GaN HEMTs with efficiencies above 60% up to 100 V for next generation mobile communication 100 W power bars

We present a systematic study of epitaxial growth, processing technology, device performance and reliability of our GaN HEMTs manufactured on 3-inch SiC substrates. Epitaxy and processing are optimized for both performance and reliability. The deposition of the AlGaN/GaN HEMT epitaxial structures is designed for both low background carrier concentration and a low trap density in order to simultaneously achieve a high buffer isolation and low DC to RF dispersion. Device fabrication is performed using standard processing techniques involving both electron-beam and stepper lithography. The developed HEMTs demonstrate excellent high-voltage stability, high power performance and large power added efficiencies. Devices exhibit two-terminal gate-drain breakdown voltages in excess of 160 V (current criterion 1 mA/mm) across the entire 3-inch wafer with parasitic gate and drain currents well below 1 mA/mm when biased up to 80 V drain bias under pinch-off conditions. Load-Pull measurements at 2 GHz on 800 μm gate periphery devices return both a well-behaved relationship between bias-voltage and output-power as well as power-added-efficiencies beyond 60% up to UDS = 100 V. For a drain bias of 100 V an output-power-density around 22 W/mm with 26 dB linear gain is obtained. On large periphery devices (32 mm gate width packaged in industry-standard ceramic packages) an output power beyond 100 W is achieved with a PAE above 50% and a linear gain around 15 dB. Reliability is tested on devices having a gate periphery of 8×60 μm at an operating bias of 50 V under both DC and RF conditions. About 10% drain-current change under DC-stress (50 mA/mm) is observed after more than 1000 h of operation with an extrapolated drain-current degradation below 20% after 200,000 h (more than 20 years) of operation. Under RF stress (2 GHz, 1 dB compression) the observed change in output power density is below 0.2 dB after more than 1000 h. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)