Photoluminescence(PL)characteristics of the structure consisting of green InGaN/GaN multiple quantum wells(MQWs)and low indium content InGaN/GaN pre-wells are investigated.Several PL peaks from pre-wells and green InG...Photoluminescence(PL)characteristics of the structure consisting of green InGaN/GaN multiple quantum wells(MQWs)and low indium content InGaN/GaN pre-wells are investigated.Several PL peaks from pre-wells and green InGaN/GaN MQWs are observed.The peak energy values for both pre-wells and green InGaN/GaN MQWs display an S-shaped variation with temperature.In addition,the differences in the carrier localization effect,defect density,and phonon-exciton interaction between the pre-wells and green InGaN/GaN MQWs,and the internal quantum efficiency of the sample are studied.The obtained results elucidate the mechanism of the luminescence characteristics of the sample and demonstrate the significant stress blocking effect of pre-wells.展开更多
In order to clarify the origin of the efficiency droop effect in InGaN based blue multiple-quantum-well(MQW)light emitting diodes(LEDs),a reasonable model is set up,taking all the possible factor(carrier delocalizatio...In order to clarify the origin of the efficiency droop effect in InGaN based blue multiple-quantum-well(MQW)light emitting diodes(LEDs),a reasonable model is set up,taking all the possible factor(carrier delocalization,carrier leakage and Auger recombination)into account.By fitting the external quantum efficiency-injection current(η–Ⅰ)measurements of two LED samples,the validity of the model is demonstrated.The fit results show that the main origin of efficiency droop at a high injection current is carrier leakage.Furthermore it is also indicated that carrier delocalization plays an important role in the efficiency droop effect in those LEDs of large localization degree.展开更多
Carrier transport via the V-shaped pits （V-pits） in InGaN/GaN multiple-quantum-well （MQW） solar cells is numer- ically investigated. By simulations, it is found that the V-pits can act as effective escape paths fo...Carrier transport via the V-shaped pits （V-pits） in InGaN/GaN multiple-quantum-well （MQW） solar cells is numer- ically investigated. By simulations, it is found that the V-pits can act as effective escape paths for the photo-generated carriers. Due to the thin barrier thickness and low indium composition of the MQW on V-pit sidewall, the carriers entered the sidewall QWs can easily escape and contribute to the photocurrent. This forms a parallel escape route for the carries generated in the fiat quantum wells. As the barrier thickness of the fiat MQW increases, more carriers would transport via the V-pits. Furthermore, it is found that the V-pits may reduce the recombination losses of carriers due to their screening effect to the dislocations. These discoveries are not only helpful for understanding the carrier transport mechanism in the InGaN/GaN MQW, but also important in design of the structure of solar cells.展开更多
Ag纳米粒子的形貌对InGaN/Ga N多量子阱(MQWs)的光致发光(PL)效率有着显著影响。本文采用离子束沉积(IBD)技术将Ag沉积在InGaN/Ga N MQWs上,然后通过快速热退火处理制备Ag纳米粒子。通过改变Ag的沉积时间获得了具有不同Ag纳米粒子形貌...Ag纳米粒子的形貌对InGaN/Ga N多量子阱(MQWs)的光致发光(PL)效率有着显著影响。本文采用离子束沉积(IBD)技术将Ag沉积在InGaN/Ga N MQWs上,然后通过快速热退火处理制备Ag纳米粒子。通过改变Ag的沉积时间获得了具有不同Ag纳米粒子形貌的样品。用原子力显微镜对各样品的Ag纳米粒子形貌和尺寸进行了表征,并且测试了吸收谱、室温和变温PL谱及时间分辨光致发光(TRPL)谱。结果表明:随着Ag沉积时间的延长,所得Ag纳米粒子粒径增大,粒子纵横比先增大后减小且吸收谱峰红移。由于不同形貌的Ag纳米粒子在入射光作用下产生的局域表面等离激元(LSPs)与MQWs中激子耦合强度不同,光发射能力也不同,与没有Ag纳米粒子的样品相比,沉积时间为15 s的样品室温PL积分强度被抑制6.74倍,沉积时间为25 s和35 s的样品室温PL积分强度分别增强1.55和1.72倍且峰位发生红移,沉积时间为45 s的样品室温PL积分强度基本没有变化。TRPL与变温PL的测试结果证明,室温PL积分强度的改变是由于LSPs与MQWs中的激子耦合作用引起的。纵横比大且吸收谱与MQWs的PL谱交叠大的Ag纳米粒子能够更好地增强InGaN/Ga N MQWs的发光。展开更多
基金Project supported by the Science Challenge Project,China(Grant No.TZ2016003)National Key Research and Development Program of China(Grant Nos.2016YFB0400803 and 2017YFE0131500)the Fund from the State Key Laboratory of Optoelectronic Materials and Technologies,Sun Yat-sen University,China。
文摘Photoluminescence(PL)characteristics of the structure consisting of green InGaN/GaN multiple quantum wells(MQWs)and low indium content InGaN/GaN pre-wells are investigated.Several PL peaks from pre-wells and green InGaN/GaN MQWs are observed.The peak energy values for both pre-wells and green InGaN/GaN MQWs display an S-shaped variation with temperature.In addition,the differences in the carrier localization effect,defect density,and phonon-exciton interaction between the pre-wells and green InGaN/GaN MQWs,and the internal quantum efficiency of the sample are studied.The obtained results elucidate the mechanism of the luminescence characteristics of the sample and demonstrate the significant stress blocking effect of pre-wells.
基金by the National Basic Research Program of China under Grant Nos 2011CB301902 and 2011CB301903the National High-Technology Research and Development Program of China under Grant Nos 2011AA03A112,2011AA03A106,and 2011AA03A105+2 种基金the National Key Technology Research and Development Program of the Ministry of Science and Technology of China(No 2011BAE01B07)the National Natural Science Foundation of China under Grant Nos 60723002,50706022,60977022 and 51002085the Beijing Natural Science Foundation under Grant No 4091001.
文摘In order to clarify the origin of the efficiency droop effect in InGaN based blue multiple-quantum-well(MQW)light emitting diodes(LEDs),a reasonable model is set up,taking all the possible factor(carrier delocalization,carrier leakage and Auger recombination)into account.By fitting the external quantum efficiency-injection current(η–Ⅰ)measurements of two LED samples,the validity of the model is demonstrated.The fit results show that the main origin of efficiency droop at a high injection current is carrier leakage.Furthermore it is also indicated that carrier delocalization plays an important role in the efficiency droop effect in those LEDs of large localization degree.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61564007 and 11364034)the Sci-Tech Support Plan of Jiangxi Province,China(Grant No.20141BBE50035)
文摘Carrier transport via the V-shaped pits （V-pits） in InGaN/GaN multiple-quantum-well （MQW） solar cells is numer- ically investigated. By simulations, it is found that the V-pits can act as effective escape paths for the photo-generated carriers. Due to the thin barrier thickness and low indium composition of the MQW on V-pit sidewall, the carriers entered the sidewall QWs can easily escape and contribute to the photocurrent. This forms a parallel escape route for the carries generated in the fiat quantum wells. As the barrier thickness of the fiat MQW increases, more carriers would transport via the V-pits. Furthermore, it is found that the V-pits may reduce the recombination losses of carriers due to their screening effect to the dislocations. These discoveries are not only helpful for understanding the carrier transport mechanism in the InGaN/GaN MQW, but also important in design of the structure of solar cells.
文摘Ag纳米粒子的形貌对InGaN/Ga N多量子阱(MQWs)的光致发光(PL)效率有着显著影响。本文采用离子束沉积(IBD)技术将Ag沉积在InGaN/Ga N MQWs上,然后通过快速热退火处理制备Ag纳米粒子。通过改变Ag的沉积时间获得了具有不同Ag纳米粒子形貌的样品。用原子力显微镜对各样品的Ag纳米粒子形貌和尺寸进行了表征,并且测试了吸收谱、室温和变温PL谱及时间分辨光致发光(TRPL)谱。结果表明:随着Ag沉积时间的延长,所得Ag纳米粒子粒径增大,粒子纵横比先增大后减小且吸收谱峰红移。由于不同形貌的Ag纳米粒子在入射光作用下产生的局域表面等离激元(LSPs)与MQWs中激子耦合强度不同,光发射能力也不同,与没有Ag纳米粒子的样品相比,沉积时间为15 s的样品室温PL积分强度被抑制6.74倍,沉积时间为25 s和35 s的样品室温PL积分强度分别增强1.55和1.72倍且峰位发生红移,沉积时间为45 s的样品室温PL积分强度基本没有变化。TRPL与变温PL的测试结果证明,室温PL积分强度的改变是由于LSPs与MQWs中的激子耦合作用引起的。纵横比大且吸收谱与MQWs的PL谱交叠大的Ag纳米粒子能够更好地增强InGaN/Ga N MQWs的发光。
