Abstract
In this paper, the photoluminescence spectra of excitons in ZnO/ZnMgO/ZnO double asymmetric quantum wells grown on a–plane substrates with internal electric-field bands structures were studied. In these structures, the electron and the hole in the exciton are spatially separated between neighbouring quantum wells, by a ZnMgO barrier with different thickness. The existence of an internal electric field generates a linear potential and, as a result, lowers the energy of quantum states in the well. For the wide wells, the electrons are spatially separated from the holes and can create indirect exciton. To help the understanding of the photoluminescence spectra, for single particle states the 8 k·p for wurtzite structure is employed. Using these states, the exciton in the self-consistent model with 2D hydrogenic 1s–like wave function is calculated.
Highlights
In the last decade, there has been a rapid progress in studies of wide bandgap semiconductors, with zinc oxide (ZnO) drawing special attention for its unique and very promising physical properties
We have carried out a comparative study of asymmetric double QWs structures with different QW widths and with different ZnMgO barriers grown on a–plane Al2O3 substrates using PL spectroscopy
The analysis is supported by single particle (SP) calculation using an 8 k·p wurtzite model in the real geometry of the samples
Summary
There has been a rapid progress in studies of wide bandgap semiconductors, with zinc oxide (ZnO) drawing special attention for its unique and very promising physical properties. High thermal conductivity and high exciton binding energy (60 meV at room temperature) [1] are some of the most important properties that can be utilized in optoelectronics, piezoelectric devices, transparent and spin electronics and in chemical sensor applications. Zinc oxide has been an intensively researched material for many years, mainly due to the fact that it is considered as an alternative, and competitive, solution to gallium nitride. Transition metal dichalcogenides, especially those with metals from group 4 of the periodic table because of energy bandgaps in the range 0.2–2 eV, could not be a direct competitors to the blue-emitting devices
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