Modelling and growth of boron containing alloys of III-Nitrides for their application in the ultraviolet range
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Date
2023
Authors
O'Connor, Thomas
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Publisher
University College Cork
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Abstract
III-Nitride semiconductor materials such as AlN, GaN, InN and their alloys, can emit light from the infrared to the deep ultraviolet region. Strong polarisation fields and significant differences in the optimum growth conditions for these binary compounds, make it difficult to understand these materials. BN is a relatively new material in this group which has the potential to improve strain engineering, increase the flexibility of bandgap engineering along with reducing the overall polarisation charge when alloyed with other III-Nitride materials.
In this work, the Schrödinger equation was solved for a single quantum well system consisting of BxGa1-xN/ AlyGa1-yN and to understand the impact BN had on the wavefunction overlap along with the emission energy.
Incorporation of wz-BN with GaN thin layers appears to prevent plastic relaxation of these layers with respect to their substrate and at higher temperatures resulting in phase separation of the material. A mechanism for recognising this clustering of boron atoms in the material is proposed using X-ray diffraction is presented.
B(Al)GaN/AlGaN multiple quantum wells (MQWs) were grown and excited by photoluminescence (PL), and emission wavelengths between 328-349 nm were obtained. The incorporation of the lowest amounts of wurtzite-BN appears to result in a redshift and an improvement in the PL emission intensity of the material. However, this benefit comes at the cost of nanovoids/ nanopits forming in the material under the growth conditions used. Nanomasking effects dominate for the smallest levels of BN incorporation, with higher degrees of disorder, propagating into the barrier regions, being observed as the B/III ratio increased, as well as a reduction in the PL intensity. To our knowledge, this is the first report of both a ternary and quaternary B(Al)GaN/AlGaN MQW stacks grown by MOCVD on a c-plane AlN/sapphire templates for UV emission.
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Keywords
BGaN , Photoluminescence , X-ray diffraction , MOCVD , MOVPE , Scanning electron microscopy
Citation
O'Connor, T. D. 2023. Modelling and growth of boron containing alloys of III-Nitrides for their application in the ultraviolet range. PhD Thesis, University College Cork.