The coupling between two heterogeneous InAs quantum dot families and its effect into optical properties
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The coupling between two heterogeneous InAs quantum dot families and its effect into optical properties Debabrata Das, Debiprasad Panda, Harshal Rawool, Vinayak Chavan, Subhananda Chakrabarti* Center for Nanoelectronics, Department of Electrical Engineering Indian Institute of Technology, Bombay Mumbai- 400076, India *Corresponding author: E-mail: [email protected]
Abstract: In this study, we present the coupling between InAs submonolayer (SML) and stranski krastanov (SK) quantum dots (QDs). Interaction between these two different dot families has been manipulated by changing the capping layer thickness. Significant shift in photoluminescence (PL) peak is observed due to the coupling effect. The dynamics of the carriers in this mixed dot matrix has also been modified, which is evident from the increasing activation energy with increasing thickness of the capping layer. Moreover, an ex situ annealing study at different temperatures has been done to check the thermal stability of the as-grown samples. Annealing at lower temperatures, improves the crystal quality a bit, but higher annealing temperatures accelerate the In-Ga interdiffusion and form smaller dots, which is visible from a blue shift in the PL peak of annealed samples. Also, this thermal process improves the dot size distribution. Introduction: Coupled QD heterostructures are widespread in the field of QD based optoelectronic transducers and devices [1]. This growth strategy is well accepted due to its improved optoelectronic performances like sharp luminescence peak, response in the optical communication window, correlated carriers transition, existence entangled quantum states, etc [1]. The coupling between vertically stacked QDs as well as in plane coupled QDs has been investigated extensively [1]. These artificially entangled QDs are incorporated into various devices like, photodetector, LED, LASER, solar cell, etc. All the efforts still reported are coupling between similar dot families [2-4]. Here we have tried coupling between two heterogeneous QD families. The seed layer has been modified into SML QDs, on top of which standard SK QDs have been grown with varying capping thickness. Propagation of stain from seed to top layer governs the self-assembly of SK QD layers. Here, by varying the submonolayer
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thickness, period of SML QDs and thickness of intermediate barrier, the upper SK dot density and size distribution can be manipulated. Also the dynamics of carriers transition in this mixed QD assembly can be engineered by controlling the tunneling of carriers from SML to SK. Three basic structures have been prepared by epitaxial growth process and characterized by luminescence spectroscopy. Also the thermal stability of as grown samples is investigated through ex situ rapid thermal annealing. Experimental Procedure: All he
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