Strain detection in crystalline heterostructures using bidimensional blocking patterns of channelled particles


Strain is a critical parameter affecting the growth and the performance of many semiconductor systems but, at the same time, the accurate determination of strain profiles in heterostructures can be challenging, especially at the nanoscale. Ion channelling/blocking is a powerful technique for the detection of the strain state of thin films, normally carried out through angular scans with conventional particle detectors. Here we report the novel application of position sensitive detectors for the evaluation of the strain in a series of AlInN/GaN heterostructures with different compositions and thicknesses. The tetragonal strain is varied from compressive to tensile and analysed through bidimensional blocking patterns. The results demonstrate that strain can be correctly quantified when compared to Monte Carlo channelling simulations, which are essential because of the presence of ion steering effects at the interface between the layer and the substrate. Despite this physical limitation caused by ion steering, our results show that full bidimensional patterns can be applied to detect fingerprints and enhance the accuracy for most critical cases, in which the angular shift associated to the lattice distortion is below the critical angle for channelling.



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Redondo-Cubero, A; David-Bosne, E; Wahl, U; Miranda, P; da Silva, MR; Correia, JG; Lorenz, K

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Authors thank fruitful discussions and support from PJM Smulders (University of Groningen). We thank S Fernandez-Garrido (Paul-Drude-lnstitute) and IM Watson (University of Strathclyde) for providing the samples for this study, as well as the detailed sample classification by S Magalhaes (Universidade de Lisboa). This work is supported by SFRH/BD/95865/2013, investigador FCT, and Ramon y Cajal programs (under contract number RYC-2015-18047), as well as FCT projects PTDC/CTM/100756/2012, CERN/FIS-NUC/0004/2015, and CERN-FIS-PAR-0005-2017. We further acknowledge the MEDIPIX-CERN collaboration to make available the detector used in this work.

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