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21 February 2018 Highly efficient InAs/InGaAs quantum dot-in-a-well heterostructure validated with theoretically simulated model
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Quantum dots based devices suffer certain disadvantages like low quantum efficiency, smaller absorption co-efficient and high dark current. Dot-in-a- well heterostructures (DWELL) offers tuning of detection peak wavelength, low dark current and higher operating temperature with optimized quantum well thickness. In this report, we correlate the optoelectronics properties of 3 different DWELL structures namely samples A, B and C having SRL thickness of 4, 6 and 8 nm, respectively with concentration-dependent theoretical model. A blue shift of around 24 nm with a decrease in PL intensity is observed as the capping thickness increases above 6 nm. Full width at Half Maximum (FWHM) decreases from B to C. These are attributed to the presence of large number of defect states and the formation of InGaAs wells with dissolution of dots in C. Low temperature PL measurement at 2.54W/cm2 and Photoluminescence Excitation (PLE) spectrum validate the presence of InGaAs wells peak at 1094.4nm for C. All samples exhibited peak spectral response at 7.56 μm. A concentration-dependent theoretical model using the Schrödinger equation was developed to calculate ground-state and inter-sub band energy-levels. The developed model shows great agreement with experimentally observed peaks from PL, PLE and spectral response. The same model was used to calculate the energy levels for InGaAs well. Based on the InGaAs experimental peak at 1.134 eV, average In concentration in the well was calculated to be around 30%.
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H. Ghadi, S. Dubey, P. K. Singh, M. Bhatt, and S. Chakrabarti "Highly efficient InAs/InGaAs quantum dot-in-a-well heterostructure validated with theoretically simulated model", Proc. SPIE 10543, Quantum Dots and Nanostructures: Growth, Characterization, and Modeling XV, 105430S (21 February 2018);

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