AlScN - a novel barrier material for GaN based rf transistors

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Besides silicon, wurtzite III-Nitride semiconductors (InN, GaN, AlN) are one of the most important class of semiconductors for electronic industry. Especially electronic devices in modern information and communication technology are strongly dependent on the polarization and its differences at heterostructures. For efficient III-N/GaN heterostructures the increase of the polarization gradient is inevitable to achieve lower sheet resistance in heterostructures, is, however, practically limited due to simultaneously increasing lattice mismatch and defect generation at interfaces.The proposed project focus on the investigation of the insufficient explored materials system Al(Ga)ScN as barrier material for a novel concept for GaN based rf transistors. AlScN solid solutions with 18% ScN are lattice matched to GaN and exhibit the same wurtzite structure as GaN. In addition, by adding Ga in quaternary AlGaScN barriers, the range of lattice matched growth can be expanded. Theoretical considerations proof in principle the suitability of Al(Ga)ScN for novel transistor structures, an experimental verification, however, has not been demonstrated yet.In the proposed project (i) single crystalline Al(Ga)ScN films shall be grown by molecular beam epitaxy in order to (ii) determine relevant materials parameter. Based on these parameters, (iii) heterostructures will be modeled and (iv) appropriate designs for rf-transistors developed. Transistor heterostructures will (v) be grown with systematically tuned AlScN barriers in order to (v) realize transistor devices. Finally, (vii) the potential of the transistor concept will be evaluated for further development of marketable rf devices.