局域表面等离激元对InGaN/GaN多量子阱发光效率的影响

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。

Influence of Localized Surface Plasmons on The Photoluminescence Efficiency of InGaN/GaN Multiple Quantum Wells

The morphology of Ag nanoparticles influences the photoluminescence (PL) efficiency of InGaN/GaN multiple quantum wells (MQWs) dramatically.In this paper,the ion beam deposition (IBD) technique was employed to deposit Ag on the surface of InGaN/GaN MQWs,and then Ag nanoparticles were fabricated by thermal annealing process.Ag nanoparticles with different morphology were obtained by adjusting the deposition time.For each sample,the morphology of Ag nanoparticles was characterized by AFM.In addition,the absorbance spectra,room and variable temperature PL spectra and time resolved PL (TRPL) spectra were carried out to determine the optical properties of the samples.The results show that the diameters of Ag nanoparticles increase with the increasing of deposition time,and the aspect ratio increases first and then decreases.Moreover,a red shift of the absorption peak of Ag nanoparticles is observed.Compared with the sample without Ag nanoparticles,the room temperature PL integrated intensity of the sample with Ag deposition time of 15 s is suppressed 6.74 times.For the samples with Ag deposition time of 25 s and 35 s,the PL integrated intensities are enhanced 1.55 and 1.72 times,respectively.Meanwhile,a red shift occurs in the peak position.Whereas,there is no obvious change in PL integrated intensity for the sample with Ag deposition time of 45 s.This phenomenon can be attributed to the difference morphology of Ag nanoparticles on each sample.The morphology of Ag nanoparticles influences the coupling strength between the localized surface plasmons (LSPs) in Ag nanopaticles and the excitons in MQWs.The light scatting ability of Ag nanoparticles is also influenced by its morphology.The measurement results of TRPL and variable temperature PL demonstrate that the change of room temperature PL integrated intensity is induced by the coupling between LSPs and the excitons in MQWs.Finally,it is found that Ag nanoparticles with bigger aspect ratio and absorption spectrum overlap PL spectrum of MQWs more can better enhance the PL intensity of InGaN/GaN MQWs.