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氧化锌基激光器件的设计、制备与特性研究
倪佩楠
学位类型博士
导师单崇新
2014-07
学位授予单位中国科学院大学
学位专业凝聚态物理
摘要氧化锌(ZnO)材料由于其大的激子结合能(60 meV)和优异的光电特性是实现高效紫外发光和低阈值紫外激光的理想材料。针对目前ZnO基电泵浦激光器件方面的不足和存在的关键问题,本论文通过等离子辅助分子束外延技术和射频磁控溅射等技术制备了ZnO基电泵浦激光器件,并对其激光特性进行了研究。本论文通过结构设计和对非平衡载流子注入机制的研究,显著改善了此类激光器件的工作性能和输出特性,取得的主要成果如下:(1)针对目前报道的ZnO 金属-绝缘层-半导体(MIS)结构随机激光阈值电流电压过高、输出模式无法调控等问题,本文通过加强此类器件结构中的光反馈机制和模式耦合,以及引入光场和电场的限制改善了其随机激光特性。基于此思想:首先通过在MIS结构中引入了FP谐振腔的方式增加了在垂直方向上的光反馈,从而降低了该器件的工作阈值、减少了在垂直方向上的随机模式数量;通过在MIS结构中引入条形波导阵列结构的方式在体系中引入了光场和电场的限制,并利用条形间的模式耦合改善其随机激光模式特性,证实此方法可以有效的提高器件的随机激射效率和降低阈值电压以及改善输出模式特性。(2)针对目前ZnO发光和激光器件中难以在有源层内实现高效的非平衡空穴注入以及MIS结构碰撞离化工作方式需要较高电压的问题,提出了利用在固体结构中得到的加速电子作为激发源来激发ZnO的方法,为ZnO有源层内同时提供非平衡空穴和非平衡电子。基于这一思路,制备了多种器件结构,得到了ZnO的发光和激光,证实了这一方法的可行性。为了进一步改善此类器件的随机激光特性,引入ZnO条形波导阵列的方式加强电场和光场的限制以及利用条形间的模式耦合,明显降低其阈值电压和电流,改善了随机激光的输出特性。同时证明了通过这一原理向ZnO中提供非平衡空穴所需的工作电压要远低于MIS结构中依靠绝缘层内碰撞离化过程所需的电压。(3)针对实现MgZnO材料的电致发光及激光器件所面临的n型和p型掺杂困难的问题,提出了利用固体结构中的加速电子激发的方式在MgZnO中同时产生电子-空穴非平衡载流子,进而实现电致发光和激光器件。基于此思想,通过不同的器件结构设计先后获得了328 nm的电致发光和285 nm的深紫外发光器件,并在较高的电压下得到了330 nm附近的随机激光输出。为了降低此类器件的工作电压以及改善器件的性能,通过在生长过程中引入富Zn条件的方法制备出了电阻率较低的MgZnO薄膜,并利用此薄膜作为发光层在较低的工作电压下在360 nm附近实现了随机激光输出。
其他摘要Znic Oxide (ZnO) featured by its large exiton binding energy (60 meV) and its excellent optoelectronic properties is one of the best materials for high efficient ultraviolet (UV) light emitting devices and low-threshold lasers. Aiming at the shortage and the key problems in the current development of ZnO based electrically pumped lasers, in this dissertation, ZnO based electrically pumped lasers have been designed and fabricated via plasma assisted molecular beam epitaxy and radio frequency magnetron sputtering, and their characteristics have been studied. It is proved that both the performance and the output characteristics of this kind of lasers can be greatly improved by properly designing the device structure as well as by studying the injecting mechanism of the non-equilibrium carriers. The research results are achieved as follows:(1) In view of the problems of the presently reported ZnO MIS random lasing structures, such as high threshold current and voltage, uncontrolled output modes, we have improved the performance of this kind of lasers by enhanceing the optical feedback mechanism and mode coupling as well as by introducing the confinement of both the optical field and the electric filed. We firstly prove that introducing the FP cavity into the MIS structure, which can enhance the optical feedback in the vertical direction, will lower the threshold and reduce the number of the random patterns in this direction. Moreover, we also prove that since the ZnO stripe waveguide arrays can introduce the confinement of both the optical field and the electric filed as well as mode coupling into the MIS structure, it can effectively increase its lasing efficiency, reduce the threshold and improve the output characteristics.(2) In view of the fact that presently it is very difficult to effectively inject non-equilibrium holes into the ZnO active layer and that the impact ionization process in the MIS structures requires high working voltage, we make use of the accelerated electrons which are obtained in solid structure to pump the ZnO active layer. In this way, both non-equilibrium holes and electrons can be generated in this layer. Based on this idea, we have realized UV emissions and lasing from many structures and confirmed its feasiblity. In order to further improve the random lasing characteristics, ZnO stripe waveguide arrays have been introduced which can enhance the confinement of both the optical field and the electric filed as well as bring about modes coupleing. As a result, the threshold has been reduced and the output characteristics have been improved. Moveover, we have proved that it is required much less voltage to generated holes in ZnO layer under the excitation of accelerated electrons than that through the impact ionization process.(3) In view of the difficulties of both p-type and n-type doping of MgZnO, we make use of the accelerated electrons obtained in solid structure to pump the MgZnO for UV emissions and UV lasing, which can generate both non-equilibrium holes and electrons simultaneously in this layer. Based on this idea, UV light emitting devices at around 328 nm and DUV light emitting devices at around 285 nm have been obtained. Moreover, UV lasing at 330 nm has been achieved at high voltage. In order to reduce the working votage and improve the performance, MgZnO films with low resistivity have been fabricated under Zn-rich conditions, and UV lasing at 360 nm has been obtained at low voltage.
语种中文
文献类型学位论文
条目标识符http://ir.ciomp.ac.cn/handle/181722/41453
专题中科院长春光机所知识产出
推荐引用方式
GB/T 7714
倪佩楠. 氧化锌基激光器件的设计、制备与特性研究[D]. 中国科学院大学,2014.
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