On the optical and microstrain analysis of graded InGaN/GaN MQWs based on plasma assisted molecular beam epitaxy

In this paper, c-plane stepped- and graded- InGaN/GaN multiple quantum wells (MQWs) are grown using plasma assisted molecular beam epitaxy (PAMBE) by in situ surface stoichiometry monitoring (i-SSM). Such a technique considerably reduces the strain build-up due to indium clustering within and across...

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Bibliographic Details
Published in:Optical materials express 2016-06, Vol.6 (6), p.2052-2062
Main Authors: Mishra, Pawan, Janjua, Bilal, Ng, Tien Khee, Anjum, Dalaver H., Elafandy, Rami T., Prabaswara, Aditya, Shen, Chao, Salhi, Abdelmajid, Alyamani, Ahmed Y., El-Desouki, Munir M., Ooi, Boon S.
Format: Article
Language:English
Subjects:
Accumulation
Gallium nitrides
Image transmission
Indium
Indium gallium nitrides
Microstrain
Molecular beam epitaxy
Reduction
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Summary:In this paper, c-plane stepped- and graded- InGaN/GaN multiple quantum wells (MQWs) are grown using plasma assisted molecular beam epitaxy (PAMBE) by in situ surface stoichiometry monitoring (i-SSM). Such a technique considerably reduces the strain build-up due to indium clustering within and across graded-MQWs; especially for QW closer to the top which results in mitigation of the quantum-confined Stark effect (QCSE). This is validated by a reduced power dependent photoluminescence blueshift of 10 meV in graded-MQWs as compared to a blueshift of 17 meV for stepped-MQWs. We further analyze microstrain within the MQWs, using Raman spectroscopy and geometrical phase analysis (GPA) on high-angle annular dark-field (HAADF)-scanning transmission electron microscope (STEM) images of stepped- and graded-MQWs, highlighting the reduction of ~1% strain in graded-MQWs over stepped-MQWs. Our analysis provides direct evidence of the advantage of graded-MQWs for the commercially viable c-plane light-emitting and laser diodes.
ISSN:2159-3930
2159-3930
DOI:10.1364/OME.6.002052