Analysis of Photoluminescence Efficiency of Annealed GalnNAs Quantum Well Grown by Solid Source Molecular Beam Epitaxy
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Analysis of Photoluminescence Efficiency of Annealed GaInNAs Quantum Well Grown by Solid Source Molecular Beam Epitaxy Ng Tien Khee1, Yoon Soon Fatt1,2, Fan Weijun1 1
School of Electrical and Electronic Engineering (Block S1) Nanyang Technological University Nanyang Avenue, Singapore 639798. 2 Singapore-Massachusetts Institute of Technology (MIT) Alliance, Nanyang Technological University, Nanyang Avenue, Singapore 639798.
Abstract The carrier dynamics of a 7.5 nm GaInNAs quantum well (QW) are studied by photoluminescence (PL) at a low temperature regime of 4 K to 150 K. The PL emission efficiency of the QW is initially evaluated to examine the recombination mechanisms in the QW. A dual-activation-energy model is later found to fit the integrated PL intensity vs. temperature curve better than a single-activation-energy model. The two states that correspond to the above activation energies could have resulted in a much faster PL intensity quenching in the GaInNAs QW as compared to that of a reference GaInAs QW. One of the states is identified as a localized state that traps carriers at a low temperature range of less than ~100 K. The other state has a larger quenching effect at temperatures higher than 100 K and this state is not studied in this paper. By fitting the original PL spectra with two Gaussian functions, the temperature dependent PL integrated intensity of both Gaussian functions was also studied to further characterize the GaInNAs QW. The analysis gives evidence of the localization behaviour in this QW.
Introduction Current high-speed optical communication systems require optical devices operating at 1.3 µm or 1.55 µm. InP based lasers and detectors are currently used for these purposes. However, considering the benefits of the lower cost and robust GaAs substrate, GaAsbased optical devices would be very desirable. This is in fact the current research and development trend of high-speed data link optical systems. For example, the growth of GaInNAs quantum well (QW) based laser on a GaAs substrate to form vertical-cavity surface-emitting lasers (VCSEL) [1], has received considerable attention by the engineering and scientific communities. However, due to the large atomic size differences of N and other constituent atoms in the GaInNAs material, and the use of energetic nitrogen sources, the photoluminescence efficiency of such material is very poor, as noted in many existing literatures [2]. Annealing has, therefore, become one of the critical steps to enhance the GaInNAs luminescence intensity. Strangely, the annealed GaInNAs materials does not necessarily have sufficiently strong luminescence intensity at room temperature, which is one of the requirements for the GaInNAs QW to be used for laser applications. Understanding the 1
carrier dynamics of the annealed GaInNAs QW is hence essential in providing a scientific explanation for the above behavior. This could further suggest possible approaches in improving the room temperature luminescence efficiency of an annealed GaInNAs QW.
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