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Detection of the third transition of InAs/GaAsSb quantum dots
김영호,Keun-Yong Ban,Som N. Dahal,Heather McFelea,Christiana B. Honsberg 한양대학교 세라믹연구소 2016 Journal of Ceramic Processing Research Vol.17 No.4
The optical properties of InAs quantum dots (QDs) embedded in GaAs0.92Sb0.08 barriers have been studied. The samplesstudied consist of 20 multiple layers of InAs QDs embedded in GaAs0.92Sb0.08, with each QD/barrier system separated by a 100nm GaAs spacer. No appreciable changes in the QD properties, such as size, shape, and density, are observed by ScanningTransmission Electron Microscopy (STEM) images. The δ-doping plane beneath the InAs QDs allows the occupancy of theQD electronic sub-band states to be controlled. Low temperature (77 K) Fourier Transformation-Infrared Spectroscopy (FTIR)results, using a multiple internal reflection (MIR) technique to enhance the optical path length, show intersubbandabsorption in the InAs QD area. The broad peak observed around 240 meV corresponds to the energy separation between theelectron ground state and the continuum state of the QDs. Another broad peak around 440 meV is ascribed to a transitionbetween a deep level and shallow donor level due to δ-doping as the signal increases as the doping density increases. Bandstructure calculations using an eight band k·p method are used to confirm the experimental results observed here.