Advanced Methods of Semiconductor Research Seminar – Tuesday 31st of March 2026
We cordially invite you to Advanced Methods of Semiconductor Research Seminar on Tuesday 31st of March 2026 at 13:15 in room 321, building A-1, where there will be delivered a lecture:
Optical Gain Evolution and Quantum-to-Bulk Transition in Wide Polar InGaN and AlGaN Quantum Wells
by Prof. Marta Gładysiewicz-Kudrawiec
from Department of Experimental Physics, Wrocław Tech
The lecture abstract is attached below.
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Lecture abstract:
Wide InGaN and AlGaN quantum wells (QWs) are considered as promising active regions due to their increased active volume and enhanced wavelength flexibility; however, their optical performance is strongly affected by built-in polarization fields. In this work, a systematic theoretical study of optical gain evolution in polar nitride QWs is presented for a broad range of well widths, from strongly confined (2 nm) to wide (25 nm) structures. The analysis is performed using a self-consistent Schrödinger–Poisson approach combined with a k·p band structure model and a Fermi’s golden rule formalism.A h ighly non-monotonic dependence of optical gain on QW width is identified, including the emergence of a finite dead-width regime in which the material gain remains negative due to polarization-induced electron–hole separation. With increasing carrier density, partial screening of the internal electric field is observed, leading to a restoration of wavefunction overlap and a crossover from ground-state-dominated to excited-state-dominated optical transitions. This transition is shown to govern the recovery and enhancement of optical gain in wide QWs. A direct comparison with bulk gain calculations demonstrates that, for sufficiently wide wells, the gain characteristics progressively approach the bulk limit, indicating a quantum-to-bulk transition. Differences between InGaN and AlGaN systems are attributed to variations in polarization strength and screening efficiency. The results provide physical insight into gain formation mechanisms in wide polar QWs and establish practical guidelines for the design of efficient visible and deep-UV emitters and laser devices.
