Photoluminescence (PL) measurement shows an additional peak with stronger and broader emission at lower photon energy besides the energy band gap transition emission from GaNAs epilayer grown by MOCVD. This emission is assigned as nitrogen-nitrogen interstitial defect related emission. Effect of V/III ratio during the MOCVD growth on this defect related emission peak has been investigated. The combination of optimum V/III ratio during the MOCVD growth and post-growth rapid thermal anneal (RTA) can eliminate this defect emission peak and at the same time the GaNAs’ band gap emission has been greatly improved. The PL spectra contain a single, narrow, and high intensity GaNAs’ band gap transition emission after the RTA annealing. The optimum V/III ratio for growing the GaNAs films with N content < 3.5% is around 20.
Morphology and crystal-quality of InAs/In0.53Ga0.47As/InP quantum dots (QDs) grown by
metal-organic vapor phase epitaxy (MOVPE) in N2 ambient using different growth modes have
been studied. It is found that the morphology and crystal-quality of InAs QDs are dependant on the
growth modes. After optimizing the dots’ growth modes, dots’ size dispersion and crystal-quality
are both improved greatly, resulting in the enhancement factor of ∼ 2.9 in the photoluminescence
(PL) peak-intensity from single QD. When the dots are buried, the dot size decrease compared with
the free-standing dots due to the soon capping layer deposition during dots’ being buried. The
thermal activation energy measured is comparable to the valence-band offset in the QD system
calculated by 8 kp theory model. This indicates the PL quenching induced by the interface defects is
suppressed due to the defect density lowering in the QDs grown by such optimized growth mode.
Special thanks are due to Mr. Liu Wei, who gives valuable discussion and much help in the theory part of this project. Thanks are due for Ms. Zhao Jinghua and Deny Sentosa, who give me much help in some experimental measurements for this research work. I would also thank School of Electrical & Electronic Engineering, Nanyang Technological University, for providing the financial support and inspiring research opportunity for me. Last but not the least, I would never forget to thank my wife Fu Li for her encouragement and shouldering the heavy family burden.
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