A uniform, reproducible and reliable GaN HEMT technology with breakdown
voltages in excess of 160 V delivering more than 60% PAE at 80 V

P. Waltereit1, W. Bronner1, R. Quay1, M. Dammann1, S. Müller1, R. Kiefer1, H. Walcher1, F. van Raay1, O. Kappeler1, M. Mikulla1, F. van Rijs2, T. Rödle2, S. Murad2, J. Klappe2, P. van der Wel2, P. Henriette2, B. Aleiner2, I. Blednov2, J. Thorpe3, R. Behtash3, H. Blanck3, K. Riepe3
phone: ++49 761 5159620, fax: +49 761 5159200, e-mail: patrick.waltereit@iaf.fraunhofer.de
1Fraunhofer Institute for Applied Solid State Physics, Tullastrasse 72, 79108 Freiburg, Germany
2NXP Semiconductors, Gerstweg 2, 6534 AE, Nijmegen, The Netherlands
3United Monolithic Semiconductors, Wilhelm-Runge-Strasse 11, 89081 Ulm, Germany
Keywords: GaN, HEMT, technology, reliability
Abstract
We report on device performance and reliability of our 3′′ GaN HEMT technology. AlGaN/GaN HEMT structures are grown on semi-insulating SiC substrates by MOCVD with sheet resistance uniformities better than 3%. Device fabrication is performed using standard processing techniques involving both e-beam and stepper lithography. The process technology exhibits an excellent uniformity across a single wafer as well as high reproducibility between individual wafers of the same or a different batch. Loadpull mapping of 8×400 μm gate periphery devices with 0.5 μm gate length across all 21 cells on entire 3-inch wafers yields a PAE of (60±2)% with only 2% scatter of the mean PAE from wafer to wafer. AlGaN/GaN HEMT’s demonstrate superior high-voltage stability and large efficiencies. Devices with 0.5 μm gate length exhibit two-terminal gate-drain breakdown voltages in excess of 160 V and drain currents well below 1 mA/mm when biased at 80 V drain bias under pinch-off conditions. Load-pull measurements at 2 GHz return both a linear relationship between drain bias voltage and output power as well as power added efficiencies beyond 60% up to 80 V drain bias. At 88 V an output power density of 15 W/mm with 24 dB linear gain is obtained. Reliability tests indicate a promising device stability under both radio frequency (RF) and direct current (DC) stress conditions.
 
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