极化效应对近紫光LED影响的数值模拟与分析

发布时间：2018-05-27 15:37

本文选题：近紫光发光二极管 + 极化效应　；参考：《沈阳工业大学》2016年硕士论文

【摘要】：发光二极管因在未来的固态照明市场中有潜在的应用前景得到广泛地的发展与应用。目前市场上常规的白光二极管大多以蓝光发光二极管激发YAG荧光粉为主,但由于近紫光发光二极管激发红、绿、蓝三基色荧光粉所发出的白光,具有高演色性与色稳定性的优点,因此,近紫光发光二极管在固态照明应用上仍极具潜力。目前,近紫光发光二极管的发光效率仍不佳,因为铟含量较低的氮化铟镓量子阱和井障的能隙差较小,载流子不易被局限在多重量子阱活性区中,且氮化物内部存在强烈的极化电场导致能带产生倾斜,电子和空穴波函数重叠率降低,载流子无法有效地贡献至辐射复合。本论文主要探讨极化效应对近紫光发光二极管的影响,并提出可优化其发光功率的结构设计。在近紫光发光二极管中,极化效应强烈地影响器件的光电特性。由于各磊晶层的界面间累积的极化电荷的存在会产生强大的内建电场,从而影响了发光二极管的能带结构,尤其是在量子阱中。结果极化效应使量子阱的能带倾斜,电子与空穴分别局限在量子阱的两侧,大幅度降低载流子复合机会,因此限制了发光二极管的发光功率及效率。本论文将从模拟的观点研究极化效应对氮化铟镓近紫光发光二极管的影响,并提出改善极化效应的发光二极管的结构的设计。本论文利用APSYS模拟软件研究In Ga N近紫光LED受总极化、自发极化及压电极化效应的影响,包括对发光性能、能带结构、极化电场、载流子分布以及辐射再结合速率等特性的影响。结果表明由于压电效应的存在严重地影响器件的性能,压电效应的存在使界面积累电荷,从而建立的内建电场,造成严重的能带倾斜现象,使得电子与空穴分开局现在量子阱的两侧,而导致电子与空穴波函数的重叠率降低,使器件的发光功率大大降低。同时,极化电场使得载流子输运受阻,最终导致载流子分布不均匀。也就是说,要改善器件的发光性能,需要抑制压电极化效应。此外,本论文设计可改善压电极化效应的近紫光LEDs结构,采用极化匹配的In Ga N/Al Ga In N多重量子阱与宽禁带的电子阻挡层相结合的结构设计。模拟结果表明采用了极化匹配的In Ga N/Al Ga In N作为活性区量子阱,可以降低电子溢流,具有较佳的电子与空穴波函数的重叠率,获得均匀的载流子分布和较低的俄歇复合速率等,所以器件的efficiency droop现象不明显。特别是搭配禁带宽度较大的材料作为电子阻挡层EBL,能更进一步提高量子阱对载流子的局限能力,优化发光性能。
[Abstract]:Because of its potential application prospects in the future solid state lighting market, light emitting diodes have been widely developed and applied. Most of the conventional white light diodes in the market are mostly blue light emitting diodes (YAG). However, the white light emitting red, green and blue three color phosphors produced by the near violet light emitting diodes is high. Because of the advantages of chromaticity and color stability, the near violet light emitting diodes are still of great potential in the application of solid-state lighting. At present, the luminescence efficiency of the near violet light emitting diodes is still poor, because the low indium nitride gallium quantum well and the gap difference between the well barrier are small, and the carrier is not easily confined to the active region of the multi weight well, and nitridation is not easy. There is a strong polarization electric field in the object that leads to the energy band to be tilted, the overlap of the electron and hole wave function decreases, and the carrier can not contribute effectively to the radiation compound. This paper mainly discusses the effect of polarization effect on the near violet light emitting diode, and proposes the structure design to optimize the luminous power of the light emitting diode. The polarization effect strongly affects the photoelectric properties of the devices. Due to the existence of the accumulated polarization charge between the interfaces of the epitaxial layers, a powerful internal electric field will be produced, which affects the band structure of the light-emitting diodes, especially in the quantum well. The polarization effect makes the energy band of the quantum well tilt and the electrons and holes are confined to the quantum well, respectively. On both sides, the carrier recombination opportunity is greatly reduced, so the luminous power and efficiency of the LEDs are limited. This paper will study the effect of polarization effect on the indium nitride near violet light emitting diodes from the analogue point of view, and propose the design of the structure of the light emitting diodes to improve the polarization effect. This paper uses the APSYS simulation software to study the I The effect of n Ga N near violet light on the total polarization, spontaneous polarization and piezoelectric polarization effect, including the effects on the properties of luminescent properties, energy band structure, polarization electric field, carrier distribution and radiation rebinding rate. The results show that the existence of piezoelectric effect seriously affects the performance of the device, the existence of the piezoelectric effect makes the boundary area charged. The built in electric field causes serious band tilt, which makes the electrons and holes separate from the two sides of the quantum well, which leads to the reduction of the overlap rate of the electron and hole wave function, which makes the light power of the device greatly reduced. In order to improve the luminescence performance of the device, it needs to suppress the piezoelectric polarization effect. In addition, the structure of the near purple LEDs structure of the piezoelectric polarization effect can be improved. The structure of the polarization matched In Ga N/Al Ga In N multi weight well and the wide band gap electronic barrier layer is designed. The simulation results show that the In Ga N/Al Ga of the polarization matching is adopted. As an active region quantum well, In N can reduce the electron spillage, have a better overlap rate of electron and hole wave function, obtain uniform carrier distribution and lower Auger recombination rate, so the efficiency droop phenomenon of the device is not obvious. Especially, the material with larger band gap as the electronic barrier layer EBL can be more advanced. It improves the confinement ability of quantum wells to carriers and optimizes the luminescent properties.
【学位授予单位】：沈阳工业大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TN312.8

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