Followed by the last year achievement of High Electron Mobility Transistor on highly resistive Ammono-GaN substrate, the PolHEMT project was accomplished by successful development of HEMT transistors characterized by their operating frequency exceeding 20 GHz (last year 6 GHz). The gate length and width were 0.8 µm and 2×200µm, the source to gate and gate-to-drain distance were 1.2 µm and 4 µm, respectively. The Ohmic contacts were optimized by regrowth of highly doped n+-InGaN:Si/n+-GaN:Si layers and deposition of metallization.
The maximum output current density reaches 1000 mA/mm at VGS=2V. The extracted on-state resistance Ron was about 4.4 Ω/mm. Transistor transconductance exceeded 220 mS/mm and reached maximum value for the expected range of operating points of transistors in DC mode. No measurable leakage current across the buffer layers or the substrate has been observed. During AC operation the maximum available frequency was 31GHz. The high power and high frequency performance can be further enhanced by optimizing gate design and length and formation of via hole interconnections.
The results were presented during the PRIME conference by prof. Anna Piotrowska (Institute of Electron Technology), 2-7th of October 2016, Honolulu, Hawaii and published at ECS Transactions 75(12):77-84 (September 2016).
This achievement opens a route for a complete value chain of transistor fabrication in Poland and Europe, from substrate development to the final device processing.
The PolHEMT project is carried out by members of Polish consortium ATU-PLUS, consisting of AMMONO SA, Institute of Electron Technology, Institute of High Pressure Physics, Institute of Physics, Polish Academy of Science, TopGaN Sp. z o. o., under the Applied Research Program of National Center of Research and Development contract number: PBS1/A3/9/2012.
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