MOVPE Growth and optical characterization of ZnSe/ZnS strained layer superlattices |
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| Institution: | 1. Department of Physics, Faculty of Science, Malayer University, Malayer, Iran;2. Department of Agronomy and Plant Breeding, Faculty of Agriculture, Malayer University, Malayer, Iran;1. Department of Clinical Pharmacy, College of Pharmacy, Najran University, Najran, Saudi Arabia;2. Department of Pharmaceutical Chemistry, College of Pharmacy, Najran University, Najran, Saudi Arabia;3. Department of Pharmaceutical Analytical Chemistry, Faculty of Pharmacy, Assiut University, Assiut, Egypt;1. Departamento de Física, Universidad del Valle, A.A. 25360 Cali, Colombia;2. Laboratorio de Materiales Funcionales a Nanoescala, Departamento de Ciencia de los Materiales, FCFM, Universidad de Chile, Beauchef 851, Santiago, Chile;3. Department of General Engineering, University of Puerto Rico, P.O. Box 00680, Mayagüez, Puerto Rico, USA;1. Department of Chemistry, Ferdowsi University of Mashhad, Mashhad 91779, Iran;2. Center of Nano Research, Ferdowsi University of Mashhad, Mashhad 91779, Iran;1. Department of Chemistry, Quaid-i-Azam University, Islamabad 45320, Pakistan;2. Nanosciences and Technology Division, National Centre for Physics, QAU Campus, Shahdra Valley Road, P.O. Box 2141, Islamabad 44000, Pakistan;3. Synchrotron-Light for Experimental Science and Applications in the Middle East (SESAME), P.O. Box 7, Allan 19252, Jordan;4. Department of Chemistry, Fatima Jinnah Women University, The Mall, Rawalpindi 46000, Pakistan;5. School of Natural Sciences, National University of Sciences and Technology (NUST), H-12, Islamabad, Pakistan;6. Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, Zhejiang, People’s Republic of China |
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| Abstract: | We have grown ZnSe/ZnS superlattices using low pressure MOVPE. The superlattices were grown onto a relaxed ZnSe buffer and were constituted of 45 periods. The well and barrier thicknesses were chosen from the calculation of critical thicknesses for coherent and free standing situations. Following this analysis we have grown samples with individual ZnSe, ZnS thicknesses of 3 to 9 monolayers.The optical properties of the samples were studied using photoluminescence, photoreflectance and reflectivity experiments. The results of the photoluminescence and photoreflectance experiments are consistent with a free standing model of the strain state, and a typical sketch of potential profile, describing the band structure of such superlattices is proposed. The photoluminescence linewidth is analyzed in terms of interface roughness. The asymmetry of the photoluminescence peaks is modelled using a density of state with a low energy exponential tail, due to the competition between radiative recombination and non-radiative recombination mechanisms. In some samples of lower crystalline quality, bound excitons were observed in the near band edge photoluminescence, which we attribute to impurity interdiffusion, which is favoured by crystalline defects. |
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