ZnO/Ga2O3核壳微米线的制备及高性能日盲紫外探测器的研制

Due to their broad prospects and urgent requirements in military and civilian applications, wide-band-gap semiconductor based solar-blind UV detector has become a hot research field. However, the crystal quality and phase separation problems of ternary AlGaN and ZnMgO thin films have not yet been solved, which has seriously hampered the performance of the detector. For improving the performance of solar-blind UV detector, a material that don’t need lattice-matching substrates, don’t require expensive equipments and complex doping processes to tune the band gaps of materials is needed. The band gap of Ga2O3 is 4.5 eV, which corresponds to the solar-blind ultraviolet spectral region. One-dimensional ZnO materials have good crystal qualities and high photoconductive gains, more importantly, the growth of ZnO microwire don’t need a lattice-matching substrate. So in this research project, depending on the different growth temperatures of ZnO and Ga2O3 materials, we use a one-step chemical vapor deposition method to grow one-dimensional ZnO core and Ga2O3 outer shell one after another. Relying on the special band structure of ZnO/Ga2O3 core/shell microwire, we will make a solar-blind UV detector with a high responsivity and fast response time, then clarify the carrier distribution and transport mechanisms of core-shell micronwire, make sure the role the core and shell have played in performance improvement. This work will not only provide a new structure and new idea to get high performance solar-blind UV detector, but also lay the foundation of practical one-dimensional micro-nano devices.

由于在军事和民用上广泛的应用前景与目前迫切的应用需求，基于宽禁带半导体的日盲紫外探测器已经成为光探测器研究领域的一大热点。但由于三元合金AlGaN与ZnMgO薄膜的晶体质量与分相问题仍未得到根本解决，严重制约了探测器性能的提升。本课题以提高日盲紫外探测器的性能为研究目标，提出采用一次化学气相沉积方法，利用生长温度的不同，先后生长结晶质量好、光电导增益高的一维ZnO核与禁带宽度对应于日盲紫外波段的Ga2O3壳层，制备出不依赖于衬底、不需要昂贵设备和复杂的工艺来掺杂调带隙、核层与壳层均为单晶的ZnO/Ga2O3核壳微米线。依靠ZnO核与Ga2O3壳所构成的特殊能带结构，制做具有高响应度、快速相应时间的日盲紫外探测器件，并阐明核壳微米线中载流子分布及输运机制，明确核壳微米线在探测器性能提高中所发挥的功能与起到的作用，为日盲紫外探测器的研制提供一种新结构与新思路，也为一维微纳器件的实用化奠定基础。

日盲光谱区是指波长在200～280nm波段的紫外辐射，由于太阳辐射在这一波段的光波几乎完全被地球的臭氧层所吸收，即在这个波段大气层中的背景辐射几乎为零，所以称为“日盲”。在该光谱范围内，由于具有极低的背景噪音，同红外探测技术相比, 紫外探测具有虚警率低、不需低温冷却、不扫描、告警器体积小、重量轻等优点。因此此项探测技术有着极其广泛的应用前景及应用需求，可用于紫外天文学、天际通信、火灾监控、汽车发动机监测、石油工业和环境污染的监测等。针对目前半导体日盲紫外探测器中光吸收层材料所存在的缺陷、裂纹、分相所导致的器件性能不理想的问题，申请人设计制备了单晶结构、不依赖于掺杂而调带隙的氧化锌/氧化镓核壳微米线材料。根据氧化锌与氧化镓生长温度的不同（ZnO:950℃; Ga2O3:1100℃），设计一次化学气相沉积生长方法先后生长高质量的ZnO/Ga2O3核壳微米线。核层氧化锌和壳层氧化镓都是高晶体质量的单晶，并且两种材料的界面非常陡峭，无明显界面缺陷和位错的存在。通过设计构建Ⅱ-型能带结构的核壳微米线，使壳层产生的光生载流子可以快速高效的分离，并通过不同的材料层在电极之间实现载流子传输。核层与壳层有不同的分工，各自实现不同的功能，比单一微纳结构光探测器更容易实现高响应度与快相应速度。器件的响应峰值在254 nm，明暗电流比可以达到10^6，响应度可达到1.3×10^3 A/W, 探测率为9.91×10^14 Jones，响应时间在 μs量级。