The structure and properties of GaAs layers grown by molecular-beam epitaxy at low temperature (150-250 °C) have been studied. The samples were found to contain up to 1.5 at.% extra As, which formed nano-scale clusters under annealing. The dependences of the excessive As concentration and As-cluster size and density on the growth and annealing conditions were established. LT-GaAs layers were found to have high electrical resistivity, however, our investigations of microwave absorption in a weak magnetic field revealed a characteristic signal usually attributed to the superconducting phase. It has been proved that this microwave absorption is unlikely to be due to either the arsenic clusters in LT-GaAs films or indium in the substrate, as it was assumed previously. We suggest a new hypothesis that the superconducting phase in LT-GaAs is Ga nanoclusters formed on the growth surface.

Energy relaxation dynamics in vertically coupled multi-stacked InAs/GaAs quantum dots Applied Physics Letters 110, 033107 (2017); 10.1063/1.4974221 High saturation intensity in InAs/GaAs quantum dot solar cells and impact on the realization of the intermediate band concept at room-temperature Applied Physics Letters 110, 061107 (2017); 10.1063/1.4975478 Stress-determined nucleation sites above GaAs-capped arrays of InAs quantum dots

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