1. The Role of the Built-In Electric Field in Recombination Processes of GaN/AlGaN Quantum Wells: Temperature- and Pressure-Dependent Study of Polar and Non-Polar Structures
- Author
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Kamil Koronski, Krzysztof P. Korona, Serhii Kryvyi, Aleksandra Wierzbicka, Kamil Sobczak, Stanislaw Krukowski, Pawel Strak, Eva Monroy, Agata Kaminska, Institute of Physics, Polish Academy of Sciences, Polska Akademia Nauk = Polish Academy of Sciences (PAN), University of Warsaw (UW), Institute of High Pressure Physics [Warsaw] (IHPP), Nanophysique et Semiconducteurs (NPSC), PHotonique, ELectronique et Ingénierie QuantiqueS (PHELIQS), Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes (UGA)-Institut de Recherche Interdisciplinaire de Grenoble (IRIG), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Grenoble Alpes (UGA), The research was partially supported by Polish National Science Centre (Narodowe Centrum Nauki) grants number 2016/23/B/ST5/02728 and 2016/23/B/ST7/03745, and the European Union from the European Regional Development Fund under the Operational Program: Innovative Economy, 2007–2013, and NCBR Panda2 501-D312-56-0000002
- Subjects
[PHYS]Physics [physics] ,[SPI]Engineering Sciences [physics] ,multi-quantum wells ,nitrides ,electric field ,time-resolved photoluminescence ,high-pressure spectroscopy ,General Materials Science - Abstract
In this paper, we present a comparative analysis of the optical properties of non-polar and polar GaN/AlGaN multi-quantum well (MQW) structures by time-resolved photoluminescence (TRPL) and pressure-dependent studies. The lack of internal electric fields across the non-polar structures results in an improved electron and hole wavefunction overlap with respect to the polar structures. Therefore, the radiative recombination presents shorter decay times, independent of the well width. On the contrary, the presence of electric fields in the polar structures reduces the emission energy and the wavefunction overlap, which leads to a strong decrease in the recombination rate when increasing the well width. Taking into account the different energy dependences of radiative recombination in non-polar and polar structures of the same geometry, and assuming that non-radiative processes are energy independent, we attempted to explain the ‘S-shape’ behavior of the PL energy observed in polar GaN/AlGaN QWs, and its absence in non-polar structures. This approach has been applied previously to InGaN/GaN structures, showing that the interplay of radiative and non-radiative recombination processes can justify the ‘S-shape’ in polar InGaN/GaN MQWs. Our results show that the differences in the energy dependences of radiative and non-radiative recombination processes cannot explain the ‘S-shape’ behavior by itself, and localization effects due to the QW width fluctuation are also important. Additionally, the influence of the electric field on the pressure behavior of the investigated structures was studied, revealing different pressure dependences of the PL energy in non-polar and polar MQWs. Non-polar MQWs generally follow the pressure dependence of the GaN bandgap. In contrast, the pressure coefficients of the PL energy in polar QWs are highly reduced with respect to those of the bulk GaN, which is due to the hydrostatic-pressure-induced increase in the piezoelectric field in quantum structures and the nonlinear behavior of the piezoelectric constant.
- Published
- 2022