Recent progress of ZnMgO ultraviolet photodetector

The ultra-violet(UV) detection has a wide application in both civil and military fields.ZnO is recognized as one of ideal materials for fabricating the UV photodetectors due to its plenty of advantages,such as wide bandgap,low cost,being environment-friendly,high radiation hardness,etc.Moreover,the alloying of ZnO with MgO to make ZnMgO could continually increase the band gap from ~ 3.3 eV to ~ 7.8 eV,which allows both solar blind and visible blind UV radiation to be detected.As is well known,ZnO is stabilized in the wurtzite structure,while MgO is stabilized in the rock salt structure.As a result,with increasing the Mg content,the crystal structure of ZnMgO alloy will change from wurtzite structure to rock salt structure.Therefore,ZnMgO photodetectors can be divided into three types based on the structures of alloys,namely,wurtzite-phase,cubic-phase and mixed-phase devices.In this paper,we review recent development and make the prospect of three types of ZnMgO UV photodetectors.     

Boosting the performance of crossed ZnO microwire UV photodetector by mechanical contact homo-interface barrier

One-dimensional (1D) micro/nanowires of wide band gap semiconductors have become one of the most promising blocks of high-performance photodetectors. However, in the axial direction of micro/nanowires, the carriers can transport freely driven by an external electric field, which usually produces large dark current and low detectivity. Here, an UV photodetector built from three cross-intersecting ZnO microwires with double homo-interfaces is demonstrated by the chemical vapor deposition and physical transfer techniques. Compared with the reference device without interface, the dark current of this ZnO double-interface photodetector is significantly reduced by nearly 5 orders of magnitude, while the responsivity decreases slightly, thereby greatly improving the normalized photocurrent-to-dark current ratio. In addition, ZnO double-interface photodetector exhibits a much faster response speed (～ 0.65 s) than the no-interface device (～ 95 s). The improved performance is attributed to the potential barriers at the microwire—microwire homo-interfaces, which can regulate the carrier transport. Our findings in this work provide a promising approach for the design and development of high-performance photodetectors.     

填充泡沫金属的熔盐相变蓄热过程模拟

本文以管肋式熔盐相变蓄热结构为对象,将相变材料填充入高孔隙率泡沫金属中以弥补熔盐导热系数低的缺陷。考虑周期性边界和重力方向相邻结构的影响,以三层管肋式结构代替整个系统建立多孔介质固-液相变输运三维物理数学模型。利用数值模拟方法,探讨在重力环境中,管式加热条件下相变材料蓄热过程的传热性能。揭示出相变界面随时间的演化,以及自然对流对蓄热过程的作用机制;讨论了泡沫金属、肋片参数及加热温度对蓄热能力的影响。