晶界对金刚石紫外探测器时间响应性能的影响

The influence of grain boundary on time response of diamond ultraviolet photo-detector

持续光电导现象是影响多晶金刚石紫外探测器时间响应性能的一个不利因素,它的存在会大大延长探测器的响应时间.本文在微米晶金刚石薄膜上制备了叉指电极间距分别为20μm和30μm的紫外探测器(分别称为器件A和器件B),讨论了晶界对多晶金刚石紫外探测器时间响应性能的影响.结果表明,器件A和器件B均表现出持续光电导和光电导增益现象,并且器件B比器件A更显著.分析得出,晶界缺陷可能在金刚石带隙中引入一个浅能级并起少数载流子陷阱中心的作用,导致了探测器的持续光电导现象和高增益.相比器件A,器件B电极间具有更多的晶界数量,因此器件B表现出更为显著的持续光电导和更高的光电导增益.

Persistent photoconductivity（PPC） is a deterring factor for the time response of ultraviolet photo-detectors made of polycrystalline diamond films.The existence of PPC can greatly prolong the response time of photo-detectors.In this paper,ultraviolet photo-detectors with interdigital electrode spacings of 20μm and 30μm（denoted as ＂device A＂ and ＂device B＂,respectively） are fabricated on microcrystalline diamond films,and the influences of grain boundary on time response of diamond ultraviolet photo-detectors are discussed.Results show that performances of PPC and photoconductive gain are present in the two photo-detectors,and the PPC is longer and the photoconductive gain is higher in device B than in device A.It is suggested that grain boundaries may induce a shallow level in the bandgap and act as minority carrier trapping centers,leading to PPC and high gain.There are more grain boundaries between the electrodes in device B than in device A,which hence explains the higher photoconductive gain and responsivity as well as more significant PPC in device B than in device A.