AlGaN基深紫外LED器件结构的模拟研究

发布时间：2018-02-12 04:58

本文关键词： AlGaN 多量子阱深紫外 LED 数值模拟 Crosslight APSYS 发光效率　出处：《华中科技大学》2015年硕士论文　论文类型：学位论文

【摘要】：近些年,伴随高亮度蓝光发光二极管的研究不断走向成熟,研究学者们逐渐将研究的重点向高Al组份的AlGaN基深紫外发光二极管转移。AlGaN基深紫外LED(light emitting diode)在杀菌消毒、生化探测、安全通讯,紫外固化、白光固态照明,能源以及军事探测等领域都有广阔的应用前景。目前外延生长高Al组份AlGaN基深紫外LED仍然十分困难,导致其发光效率非常低。不仅如此,随着工作电流的增加,其输出效率也会急速降低,这些都限制了其大规模的应用。因此,提高AlGaN基深紫外LED的发光性能、获得高效的深紫外LED极其重要。本论文首先简要叙述了AlGaN基深紫外LED研究背景与发展概况,器件的工作原理和相关物理特性以及Crosslight公司的半导体器件仿真软件APSYS。然后,详细介绍了利用APSYS软件自带的模型对AlGaN基深紫外LED量子阱结构和P型区电子阻挡层的设计和优化,提出了两类新型器件结构,并分别对两种结构的AlGaN基深紫外LED的光电特性进行了模拟研究:(1)分别对两层和三层阶梯型(staggered)量子阱的AlGaN基深紫外LED结构进行了仿真。通过对发光性能、能带结构、载流子分布以及辐射复合效率等特性进行分析,得出staggered量子阱的采用一方面增加了电子和空穴的波函数重叠率,另一方面使得有源区电子和空穴的浓度增加,辐射复合增强,极大地改善了器件中普遍存在的效率陡降问题,提升了发光效率,模拟结果证明三层staggered量子阱结构的发光性能更优于两层。(2)研究了三种新型的三角形电子阻挡层(组分递增型、倒V型和V型)取代传统的AlGaN电子阻挡层对AlGaN基深紫外LED发光性能的影响。通过深入分析三角形电子阻挡层(EBL,electron blocking layer)提高发光效率的不同物理机理得出,组分递增型和倒V型的三角形EBL主要是通过改善最后一个势垒与EBL之间的晶格匹配来减少界面处的极化电场;最后一种V型的三角形EBL层物理机理不同于前两种,一方面主要是因为EBL中组分渐变形成的势阱对能带的拉伸,缓解了最后一个量子势垒与EBL界面处的能带弯曲,使得电子和空穴的有效势垒高度都相应的提高和降低了,另一方面,EBL的势阱中发生了较强的空穴聚集效应。三角形电子阻挡层的采用增强了对电子的限制作用、提高了空穴注入效率,因此提升了发光效率,降低了效率陡降现象。
[Abstract]:In recent years, with the development of high brightness blue light emitting diodes, researchers have gradually shifted their research emphasis to AlGaN based deep ultraviolet light emitting diodes with high Al composition. AlGaN-based deep ultraviolet LED(light emitting diodes have been sterilizing and biochemical detection. Security communication, UV curing, white light solid state lighting, energy and military detection have broad application prospects. At present, it is still very difficult to epitaxially grow high Al component AlGaN based deep ultraviolet LED, which results in very low luminescence efficiency. With the increase of operating current, the output efficiency will decrease rapidly, which limits its large-scale application. Therefore, the luminescence performance of AlGaN based deep ultraviolet LED is improved. It is very important to obtain high efficiency deep ultraviolet LED. In this paper, the background and development of deep ultraviolet LED based on AlGaN, the working principle and related physical characteristics of AlGaN, and the semiconductor device simulation software APSYS of Crosslight Company are briefly described in this paper. The design and optimization of AlGaN based deep ultraviolet LED quantum well structure and P-type electronic barrier layer are introduced in detail by using the model of APSYS software. Two kinds of novel device structures are proposed. The optoelectronic properties of two kinds of AlGaN based deep ultraviolet LED are simulated. The AlGaN based deep ultraviolet LED structures of two-layer and three-layer stepped quantum wells are simulated, respectively. The characteristics of carrier distribution and radiation recombination efficiency are analyzed. It is concluded that the adoption of staggered quantum wells increases the overlap rate of wave functions between electrons and holes on the one hand, and increases the concentration of electrons and holes in active region on the other. The problem of sharp drop in efficiency is greatly improved and the luminescence efficiency is improved. The simulation results show that the luminescence performance of three-layer staggered quantum well structure is better than that of two-layer. The effect of inverted V and V type) on the luminescence properties of AlGaN based deep ultraviolet LED was studied by replacing the traditional AlGaN electronic barrier layer. The different physical mechanisms of improving the luminescence efficiency of the triangular electronic barrier layer (EBLelectron blocking layer) were analyzed. The incremental and inverted V-type triangular EBL decrease the polarized electric field at the interface mainly by improving the lattice match between the last barrier and the EBL, and the last V-type triangular EBL layer is different from the first two kinds of physical mechanism. On the one hand, it is mainly due to the stretching of the band in the potential well formed by the gradual change of the component in EBL, which alleviates the band bending at the interface between the last quantum barrier and the EBL, and makes the effective barrier height of the electron and hole increase and decrease accordingly. On the other hand, there is a strong hole aggregation effect in the potential well of EBL. The use of triangular electron barrier layer enhances the effect of limiting electrons and improves the efficiency of hole injection, so it improves the efficiency of luminescence and reduces the phenomenon of steep drop of efficiency.
【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN312.8

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