K/Ka - band Load-Pull performance of AIGaN/GaN/AIN HEMTs on free-standing AIN substrates

P. Gribisch¹, F. Brunner², N. Kemf¹, C. Last¹, C. Schulze¹, R. Weingärtner², S. Besendörfer², and O. Hilt¹

Published in:

Semiconductor Science and Technology, vol. 41, pp. 10LT02, doi:10.1088/1361-6641/aeaf12 (2026).

Abstract:

We demonstrate first K/Ka band CW load-pull (LP) measurements of AlGaN/GaN/AlN high electron mobility transistors (HEMTs) on free-standing AlN substrates at 20GHz and above. The AlN buffer on AlN shows a much lower dislocation density compared to the same epitaxial stack grown on SiC substrates. The devices with a gate length of 220 nm exhibit an off-state leakage current below 100 µA mm-1 and a maximum Ids of around 1 A mm-1. Measured with passively-tuned LP equipmentat 10 (20) GHz the devices with a gate width of 8× 75µm reveal up to 58 (40) % maximum power added efficiency, 14 (9) dB gain and 4.1 (2.8) W mm-1 Pout, where higher drain voltages leadto an increase in Pout. For 30GHz 33%, 7 dB and 2.6 W mm-1 were measured with an actively-tuned equipment for 4× 50µm devices. The 20 and 30 GHz measurements are to the best of ourknowledge the first reported so far for GaN HEMTs on AlN substrates underlining the potential of this material system.

Keywords:

load pull, HEMTs, HEMT, substrates, substrate, mobility, transistor, AlN, AlN-buffer, dislocation density, SiC, leakage current, efficiency, efficiencies, Lead, GaN, GaN HEMTs, GaN HEMT, GaN-HEMTs

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