Investigation of fundamental physical properties of coupled quantum well - quantum dot systems emitting in the near infrared range of 1.3 - 1.55 micrometer (Acronym: QuCoS = Quantum Coupled Systems).

• Applicant: Professor Dr. Johann Peter Reithmaier
• Subject Area: Experimental Condensed Matter Physics ; Electronic Semiconductors, Components and Circuits, Integrated Systems, Sensor Technology, Theoretical Electrical Engineering ; Synthesis and Properties of Functional Materials
• Term: from 2014 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 262304022

The subject of this research is to investigate the basic physical properties of coupled two-dimensional (quantum well) and zero-dimensional (quantum dots) semiconductor-based quantum subsystems characterized by the ground state photon emission wavelength in the near-infrared (1.3-1.55 um) spectral range. >>>> The major aim of the project is to perform the theoretical and experimental studies of several closely related issues in order to acquire the knowledge on: ---- (i) important physical interactions, which can account for a non-resonant charge/exciton/spin transfer between spatially separated but still quantum-mechanically coupled quantum well (QW) and quantum dot (QD) subsystems (e.g. electron/hole-optical/acoustic phonon, exciton-exciton or carrier-carrier interaction processes); ---- (ii) carrier/exciton/spin relaxation pathways in the QW-coupled-QD system which should primarily depend on the coupling strength and efficiency of relaxation-mediated scattering processes; ---- (iii) the influence of material composition/strain in the system on the efficiency of Auger process and Auger-assisted carrier transfer between the quantum well and the dots; ---- (iv) possibilities to control the strength of the quantum-mechanical coupling between QW and QD, taking into account such factors as e.g.: temperature, carrier/exciton population, chemical content of semiconductor materials and their electronic structure; ---- (v) coherent and incoherent dynamic properties of charge/exciton/spin transfer followed by optical injection/spin initialization process and its control in the QW-coupled-QD system; ---- (vi) spin-related properties of a coupled QW and QD system. >>>> The hypothesis we intend to verify is that by a careful selection of physical interactions and semiconductor material properties one can design and produce a quantum system with widely and precisely controllable efficiency of charge/exciton/spin transfer from a QW to the QD ground state, both separated in the real space, while keeping three conditions: (i) the QD ground state is the lowest energy state for an entire coupled system, (ii) it keeps its localized character (atomic-like character), and (iii) emits photons in the near-infrared spectral range of 1.3-1.55 um. >>>> As a long-term objective, we anticipate that the results of our investigation will point out the most critical issues related to a design of the coupled QW-QD systems of desired parameters. We intend to verify the role of a quantum mechanical coupling between spatially separated subsystems of different dimensionality and demonstrate how to control it on the basic physical level. This knowledge will possibly be used in the development of novel optoelectronic and spintronic devices of superior parameters (i.e. fast modulated lasers, switches, long storage time and fast read/write memories etc.), which rely on the QW-coupled-QD system architecture.

• DFG Programme: Research Grants
• International Connection: Israel, Poland
• Participating Person: Professor Dr. Grzegorz Sek