Polish team of engineers have been working for two years on developing the microwave technology under PolHEMT project "Microwave AlGaN/GaN HEMTs on monocrystalline GaN substrates". The main aim of this project is the development and fabrication of modern and innovative microwave GaN based High Electron Mobility Transistors for the purpose of new generation of radiolocation.
The 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.
It is a very well known fact, that one of the most important aspects of GaN transistor development is an appropriate choice of substrates. The material must allow transistors to operate at high voltage, reach higher frequencies (GHz or THz) and have excellent heat dissipation features. The consortium decided to use a macrodefects free monocrystalline gallium nitride substrates from AMMONO SA, which is in fact the world's best technology source for such type of material.
In frame of this project successful results of epitaxy and processing of AlGaN/GaN HEMT transistors deposited on low dislocation semi-insulating monocrystalline AMMONO-GaN substrates was published in paper by A. Taube et al in physica status solidi (phys. status solidi a 212, 1162 (2015), DOI: 10.1002/pssa.201431724). The AlGaN/GaN structures were grown by MOVPE, resulting in two dimensional electron gas (2DEG) density of 1.1x1013 cm-2 and mobility 1300 cm2/Vs. Then the transistor structures were processed as two-finger devices with a gate length of 1 µm and gate width of 2 x 300 µm. The source-gate and gate-drain length was 3.5 µm and 5.5 µm. The isolation of adjacent devices was done using implantation by Al+ ions. The leakage current was lower than 1 µA/mm, proving good isolation of the transistor structure. The transistors are successfully operating both in DC (IDS=800 mA/mm) and RF mode (up to 6.5 GHz).
Obtained results confirmed, AMMONO-GaN substrates may be regarded as a good alternative material (to Si and SiC substrates) for the development of high frequency transistors. The use of low dislocation GaN substrates may be a critical point in these applications, where high reliability is demanded.
After commercialization phase of the project, Poland, having highly advanced gallium nitride semiconductor know-how, will be able to build latest generation radars for short- and medium-range national missile defence system.
For further details please contact our team.