21 February 2018 Co-relation of theoretical simulation with experimental results for InAs quantum-dot heterostructures with different capping material
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Quantum dot(QD) based devices are capped with various strain reducing layers in order to improve quality of dots by low surface diffusion and increase detection to long wavelength infrared region(LWIR). We present a model for the effect of various strain reducing layers on quantum dot heterostructures and study the corresponding variation in optoelectronic properties viz. photoluminescence (PL), photoluminescence excitation (PLE) and device characteristics of the samples. Schrödinger equation was used in the concentration dependent model in order to calculate ground state and inter-sub band energy-levels. Three InAs QD (2.7 ML) samples with different capping GaAs (Sample A), 6 nm In0.15Ga0.85As (Sample B) and 6 nm In0.15Ga0.85As DWELL (Sample C with 2 nm pseudomorphic layer of In0.15Ga0.85As) were grown. Low temperature (8 K) PL spectra exhibits ground state peak at 1112.62, 1150 and 1166.93 nm for samples A, B and C, respectively. PLE measured at 8 K exhibited first and second excited state peaks at 1046.15 nm, 991.59 nm for Sample A, 1079nm and 1003nm for Sample B and 1095.55nm and 1034.51nm for Sample C. Highest absolute area measured using temperature dependent PL (photocurrent) was observed for sample B which can be justified by increment in quantum dots formation thus resulting higher quantum yield. Single pixel detectors were fabricated and sample B yielded lowest dark current density at 80 K. A multicolor spectral response was observed from sample B with corresponding peaks at 5.13 and 7.53 μm. The calculated energy levels are in good agreement with experimental results (PL and PLE). Spectral response peaks observed from all samples were successfully matched to the energy levels calculated from the simulation.
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H. Ghadi, P. K. Singh, S. Dubey, M. Bhatt, S. Chakrabarti, "Co-relation of theoretical simulation with experimental results for InAs quantum-dot heterostructures with different capping material", Proc. SPIE 10543, Quantum Dots and Nanostructures: Growth, Characterization, and Modeling XV, 105430R (21 February 2018); doi: 10.1117/12.2289465; https://doi.org/10.1117/12.2289465

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