Recombination Dynamics of InGaN/GaN Multiple Quantum Wells With Different Well Thickness
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Recombination Dynamics of InGaN/GaN Multiple Quantum Wells With Different Well Thickness X. C. Wei, L. Zhang, N. Zhang, J. X. Wang and J. M. Li Research and Development Center for Solid State Lighting, Institute of Semiconductors, Chinese Academy of Sciences, State Key Laboratory of Solid State Lighting, Beijing Engineering Research Center for the 3rd Generation Semiconductor Materials and Application, Beijing 100083, People's Republic of China ABSTRACT Recombination dynamics of InGaN/GaN multiple quantum wells (MQWs) with different well thickness have been studied. From the behaviour of temperature dependent photoluminescence, we find that the activation energy decreases with the well thickness increasing. In addition, with temperature changing from 10K to room temperature, the “W” shape of full width of half maximum is also thickness related, and it becomes more obvious with the well thickness increasing. These results indicate that the dominant recombination dynamics change from exciton localization to quantum confined stark effect with well thickness increasing. From our measurement, the InGaN/GaN MQWs with 3nm thickness seems a turning point, which shows the best optimized optical and structural properties. INTRODUCTION GaN-based multiple quantum wells have been attracting lots of attention as the key material for the fabrication of high brightness light emitting diodes (LEDs) and continuous wave (cw) laser diodes because of the advantage of tuning ability of the full spectrum. [1, 2] The 254 lm/W LED and InGaN/GaN MQW LDs with a life time of more than 10,000 hours for cw operation at room temperature have already been reported. But in contrast to the striking technology development, the underlying emission mechanism of these devices is still not fully understood. Two different radiative recombination mechanisms are generally accepted for InGaN/GaN MQWs grown on the lattice-mismatched substrates. One is attributed to the exciton localization effect. Experiments showed [3] that emission from InGaN may be due to recombination of excitons localized at potential minima in the quantum well, and these exciton localizations at deep traps is mainly originated from In-rich regions acting as quantum dots. It has also been shown that the localized excitons within indium-rich regions resulting from partial phase segregation in InGaN alloys are considered to prevent them from reaching nonradiative recombination sites and play an important role for spontaneous emission. The other is related to the internal piezoelectric field induced quantum confined stark effect (QCSE) [4], which is mainly related to the strain caused by the lattice mismatch between GaN and
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InGaN. The emission peak demonstrates an anomalous blue shift with temperature increasing, and all these mechanisms and accordingly the electrical property and polarized field will be strongly influenced by the well thickness. In order to clarify the underlying physics of light emission of Nitride-based multiple quantum wells, in this study, we prepared InGaN/GaN
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