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题名	MgZnO合金薄膜带隙调制及其紫外探测器件
作者	郑剑
学位类别	硕士
答辩日期	2014-07
授予单位	中国科学院大学
导师	刘益春,张振中
学位专业	凝聚态物理
中文摘要	宽带隙半导体是现代短波长光电子技术发展的材料基础之一。对宽带隙半导体薄膜材料的制备研究和器件开发具有重要的应用价值。近十多年来，MgO-ZnO准二元合金系统得到人们越来越多的关注。该材料具有非常宽的光学带隙调制跨度（从ZnO的3.37 eV 到MgO 的7.8 eV），相应光波长从380 nm 到160 nm。然而，由于常态下ZnO和MgO倾向于不同的配位结构（ZnO是四配位的纤锌矿结构，MgO是六配位的岩盐结构），使MgZnO在较宽的组分区间难以实现可用的单一相合金，给MgxZn1?xO合金带隙工程及其应用带来了很大的挑战。本文主要针对困扰MgZnO材料制备中的结构分相问题，利用金属有机物化学气相沉积系统（MOCVD），设计优化制备工艺，实现了MgxZn1-xO合金薄膜带隙可调制范围的进一步扩展，研究了其结构、光学性质以及热稳定性，探讨了亚稳态生长机制，并实现了基于该系列薄膜的日盲紫外探测器，取得主要结果如下： 1. 在m面蓝宝石衬底上生长不同组分的MgxZn1-xO薄膜，研究了薄膜光学和结构特性随组分的演化规律，获得了(110)取向高质量立方相Mg0.45Zn0.55O薄膜。对薄膜的外延结构特点进行了分析，并应用于金属-半导体-金属（MSM）结构器件，获得了光响应峰在260 nm、光响应截止波长278 nm的日盲紫外探测器。 2. 利用低压MOCVD设备，通过优化制备工艺，在c面蓝宝石衬底上采用MgO籽晶层和组分渐变缓冲层来控制立方相MgxZn1-x O薄膜的生长，获得了Zn组分（1-x）达到0.7的单一立方相MgxZn1-xO薄膜，把MgZnO合金带隙调制范围从MgO一侧扩展到了4.5 eV以下，覆盖了整个日盲紫外波段（200-280 nm）。这种亚稳态单一立方相MgZnO合金薄膜的生长得益于缓冲层晶格模板的诱导作用和较低的生长温度。实验发现衬底温度在350-400oC区间有利于制备高Zn组分立方相MgxZn1-xO薄膜。热退火实验和相应探测器的制备测试研究表明，这种亚稳态的单一立方相MgxZn1-x O（1-x ~ 0.7）薄膜的稳定性能够满足实际应用需要。 3. 在MgO籽晶层和组分渐变缓冲层上生长了超过相变临界厚度的Mg0.29Zn0.71O薄膜，基于此样品的MSM器件光响应度比在纯立方相薄膜上制备的器件显著提高，在30 V偏压下峰值响应度可达 27.9 A/W（268 nm）。如此高响应度的MgZnO基准日盲紫外探测器尚无报导。分析认为原位生长在立方相MgZnO薄膜表面上的极薄的结构相变层引入了高密度的界面态，在器件中起到了降低电极接触电阻并增加光电导增益的作用。
英文摘要	The intense interest in shot-wavelength optoelectronic devices has promoted large research efforts into the wide bandgap semiconductors. Pseudobinary ZnO-MgO alloy system received increasing attention in the past decade, mostly attributed to its potential applications in a wide UV spectrum region from 380 nm to 160 nm promised by its possible tunable-bandgap (3.37 eV for ZnO to 7.8 eV for MgO). However, the solid solution of MgxZn1?xO is of eutectic type at normal conditions, and the restricted solid solubility poses significant challenges to the bandgap engineering. This thesis focuses on understanding and suppressing phase segregation of the MgxZn1?xO alloy films, and a technique using a compositionally-graded buffer layer and low growth temperature is developed for the growth of single cubic MgZnO alloy films with high Zn content in a LP-MOCVD system. The optical and structural properties and thermal stability of the metastable alloy films and their applications in UV detectors are studied. The main contents are as follows: [1] Single(110)-oriented cubic MgxZn1-xO alloy films with Zn content up to 55% were prepared on m-plane sapphire by using MOCVD method. The optical bandgap can be modulated to a value of 4.7 eV. The epitaxial relationships have been determined by XRD analysis and the films present good structural quality with uniform in-plane orientation. An MSM solar-blind UV photodetector was fabricated on the Mg0.45Zn0.55O thin film, which shows a sharp cutoff at 278 nm. [2] A graded quasi-homo buffer layer, composed of a MgO layer and a continuously Zn-increased MgZnO layer, was used to grow pure cubic phase MgxZn1-xO thin films on c-plane sapphire in a LP-MOCVD system. The Zn content in rocksalt MgxZn1-xO is expanded to 1-x ~ 0.7 and the optical bandgap of the film is 4.45 eV. The role of the buffer layer was discussed, and a substrate temperature range from 350 oC to 400 oC was found to be benefit to grow the metastable MgxZn1-xO films with high Zn content. The metastable cubic MgxZn1-xO films are sufficiently stable to be used in UV detectors, and thermal annealing experiments were also carried out to investigate their phase-stability. [3] An MSM solar-blind UV photodetector was fabricated on a Mg0.29Zn0.71O thin film, which shows a large responsivity of 27.9 A/W at 268 nm 30 V bias. An ultra thin phase-transition layer is regarded to lead to improvement of the metal-semiconductor contact and more internal gain . The results provide a new choice to realize high performance MgZnO-based solar-blind UV detectors.
语种	中文
公开日期	2014-08-21
内容类型	学位论文
源URL	[http://ir.ciomp.ac.cn/handle/181722/41507]
专题	长春光学精密机械与物理研究所_中科院长春光机所知识产出
推荐引用方式 GB/T 7714	郑剑. MgZnO合金薄膜带隙调制及其紫外探测器件[D]. 中国科学院大学. 2014.

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