A new research theme at IWC PAN: the OPUS 30+LAP/Weave project of Dr Piotr Kruszewski

On 12 November, the National Science Centre (NCN) announced the final results of the prestigious OPUS 30+LAP/Weave call for projects carried out with partners from Germany, released after acceptance by the German Research Foundation (DFG). The list of laureates includes 18 bilateral Polish–German projects and 3 trilateral projects which, in addition to cooperation with German partners, involve partners from Austria, Belgium-Flanders and Czechia. In total, Polish teams will receive almost PLN 37 million for these projects.

Among the awarded projects is one led by our colleague from the Laboratory of Crystallization (NL-3), Dr Piotr Kruszewski, who together with Dr Zbigniew Gałązka of the Leibniz Institute for Crystal Growth (IKZ) in Berlin will investigate point defects and their impact on electrical conductivity in β-(AlₓGa₁₋ₓ)₂O₃ crystals grown by the Czochralski method. The official title of the project is "Study of defects and their impact on electronic transport in bulk β-(AlₓGa₁₋ₓ)₂O₃ single crystals grown by the Czochralski method" (ST5 panel).

The main goal of the project is to determine the mechanisms governing the formation of defects relevant to electrical transport in bulk β-(AlₓGa₁₋ₓ)₂O₃ single crystals, including an explanation of why silicon-doped crystals show a steep drop in free electron concentration as the aluminium content ([Al]) increases from about 15 to 25 mol%. The research hypotheses of the project are that:

• silicon donors may be compensated by defects or impurities, and this compensation increases markedly with rising [Al];
• silicon donors incorporated into crystals with a high [Al] content are not as effective as theoretical calculations predict;
• the decrease in electrical conductivity results from strong phonon scattering combined with scattering on ionized dopants; and
• shallow silicon donors shift towards deep donor levels as [Al] increases.

These hypotheses will be verified at IWC PAN using a newly built measurement setup dedicated, among other things, to current-mode spectroscopic techniques that will make it possible to study active trap states in non-conducting and semi-insulating crystals and layers, where conventional capacitance-based measurements cannot be applied.

The project also involves research groups from the Faculty of Physics of the University of Warsaw, where defects will be studied by electron paramagnetic resonance (EPR), and from the Institute of Nuclear Chemistry and Technology in Warsaw, where the crystals will be irradiated with high-energy electrons in order to create precisely defined point defects and then analyse them in terms of their electrical activity and thermal stability.

The budget of the Polish part of the project amounts to PLN 2,344,300, and the project will run for 36 months.