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).
Electronic Semiconductors, Components and Circuits, Integrated Systems, Sensor Technology, Theoretical Electrical Engineering
Synthesis and Properties of Functional Materials
Final Report Abstract
The main focus of QuCoS project was to perform the fundamental theoretical and experimental studies of the coupled two-dimensional (quantum well) and zero-dimensional (quantum dots) semiconductor-based quantum subsystems. Research work involved theory, fabrication and measurements of the poorly understood in the literature coupled QW-QD systems with the ground state emission in the near-infrared (1.3-1.55 µm) spectral range. The main strength of this joint collaborative project was that the specific expertise of the four different international groups were brought together for a successful investigation of the problem and for the development of a consistent picture with a high relevance for the future potential applications. Epitaxially grown InP-based coupled QW-QD structures (their separate components as well as full tunnel structures) were investigated by different optical spectroscopy methods in order to optimize them in terms of appropriate structural and optical quality, band structure alignment, coupling strength and tunnelling efficiency. By systematic change of the different design parameters, the optimum injector InGaAs QW and barrier InAIGaAs widths could be determined. In addition, experimental findings were supported and verified by a detailed modelling of the investigated structures in the frame of 3D eight-band k p model, The project brought significantly new knowledge in the field, showing which of the system parameters are the most important for the control of quantum-mechanical coupling and the kinetics of optical processes in hybrid systems, which allow control of selected properties. As proof of concept, InP-based tunnel injection QD lasers using an optimum QW-QD design and a reference QD laser were grown, processed and compared in terms of static laser characteristics and small signal modulation bandwidth. A small signal modulation bandwidth of 8.6 GHz and a maximum digital modulation of 23 GBit/s was obtained for the TI-QD laser. To the best of our knowledge, this is the first time to record large signal modulation at high bit rates at room temperature. On the other hand, the reference laser show still a significantly higher small signal modulation bandwidth of 14.9 GHz. This higher performance of the pure QD laser is still surprising and needs further investigations in experiments and modelling. Additionally, the possibility of further improvement of internal laser parameters by a rapid thermal annealing step was studied. A strong improvement in device performance is observed after annealing in QD lasers while in TI-QD lasers no significant improvement was obtained, which might be caused by detuning of band energy alignment and different impact of the RTAprocess on the material quality of QWand QD layers. The project results clearly show how important the knowledge about the quantum mechanical properties are in the understanding of laser device properties using lowdimensional active regions. The first application of TI-QD structures with an initially optimised QW-QD design, as proposed by theory and realized in last year of the project, give clear hints on the potential and long-term perspective of this concept, e.g., high-speed large signal modulation beyond 20 GBit/s is possible. However, many aspects are still not understood (e.g. QD lasers exhibit significantly larger bandwidths) and would need a more detailed understanding and further investigations.
Publications
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Carrier dynamics in a tunneling injection quantum dot semiconductor optical amplifier, Phys. Rev. B 98 (2018) art. 125307, 1-8
Khanonkin, G. Eisenstein, M. Lorke, S. Michael, F. Jahnke, A. K. Mishra, and J. P. Reithmaier
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Carrier relaxation bottleneck in type-II InAs/InGaAlAs/InP(001) coupled quantum dots-quantum well structure emitting at 1.55 μm, Applied Physics Letters 112 (2018) art. 221901, 1-5
M. G. Syperek, J. Andrzejewski, E. Rogowicz, J. Misiewicz, S. Bauer, V. I. Sichkovskyi, J. P. Reithmaier, G. Sęk
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Carrier transfer efficiency and its influence on emission properties of telecom wavelength InP-based quantum dot - quantum well structures, Scientific Reports 8 (2018) art. 12317, 1-10
W. Rudno-Rudziński, M. G. Syperek, J. Andrzejewski, E. Rogowicz, G. Eisenstein, S. Bauer, V. I. Sichkovskyi, J. P. Reithmaier, G. Sęk
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Control of Dynamic Properties of InAs/InAlDaAs/InP Hybrid Quantum Well-Quantum Dot Structures Designed as Active Parts of 1.55 µm Emitting Lasers, Phys. Status Solidi A 215 (2018) 1700455
W. Rudno-Rudziński, M. Syperek, A. Maryński, J. Andrzejewski, J. Misiewicz, S. Bauer, V. Sichkovskyi, J.P. Reithmaier, M. Schowalter, B. Gerken, A. Rosenauer, G. Sęk
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Growth and optical characteristics of InAs quantum dot structures with tunnel injection quantum wells for 1.55 µm highspeed lasers, Journal of Crystal Growth 491(2018) 20-25
S. Bauer, V. Sichkovskyi, J.P. Reithmaier
