Parakh Mehul, Johnson Sean, Pokharel Rabin, Ramaswamy Priyanka, Nalamati Surya, Li Jia, Iyer Shanthi
Nanoengineering, North Carolina A&T State University, Greensboro, North Carolina, UNITED STATES.
Electrical and Computer Engineering, North Carolina A&T State University, Greensboro, North Carolina, UNITED STATES.
Nanotechnology. 2020 Mar 18. doi: 10.1088/1361-6528/ab80fc.
In this work, the first observation of the space charge limited conduction mechanism (SCLC) in GaAsSb nanowires (NWs) grown by Ga-assisted molecular beam epitaxial technique, and the effect of ultrahigh vacuum in-situ annealing have been investigated. The low onset voltage of the SCLC in the NW configuration has been advantageously exploited to extract trap density and trap distribution in the bandgap of this material system, using simple temperature dependent current-voltage measurements in both the ensemble and single nanowires. In-situ annealing in an ultra-high vacuum revealed significant reduction in the trap density from 1016 cm-3 in as-grown NWs to a low level of 7 * 1014 cm-3 and confining wider trap distribution to a single trap depth at 0.12 eV. A comparison of current conduction mechanism in the respective single nanowires using conductive atomic force microscopy (C-AFM) further confirms the SCLC mechanism identified in GaAsSb ensemble device to be intrinsic. Higher current observed in current mapping by C-AFM, increased 4K photoluminescence (PL) intensity along with reduced full-width half maxima and more symmetric PL spectra, reduced asymmetrical broadening and increased TO/LO mode in room temperature Raman spectra for in-situ annealed NWs again attest to effective annihilation of traps leading to the improved optical quality of NWs compared to as-grown NWs. Hence, the I-V-T analysis of the SCLC mechanism has been demonstrated to be a simple approach to obtain information on growth induced traps in the NWs.
在这项工作中,研究了通过镓辅助分子束外延技术生长的砷化镓锑纳米线(NWs)中的空间电荷限制传导机制(SCLC)的首次观察结果,以及超高真空原位退火的影响。利用NW结构中SCLC的低起始电压,通过在整体和单根纳米线中进行简单的与温度相关的电流-电压测量,有利地提取了该材料系统带隙中的陷阱密度和陷阱分布。在超高真空中进行的原位退火显示,陷阱密度从生长态NWs中的1016 cm-3显著降低到7×1014 cm-3的低水平,并将更宽的陷阱分布限制在0.12 eV的单个陷阱深度。使用导电原子力显微镜(C-AFM)对各个单根纳米线中的电流传导机制进行比较,进一步证实了在砷化镓锑整体器件中确定的SCLC机制是本征的。C-AFM电流映射中观察到的更高电流、4K光致发光(PL)强度增加以及半高宽减小和PL光谱更对称、室温拉曼光谱中不对称展宽减小和TO/LO模式增加,再次证明与生长态NWs相比,原位退火NWs中陷阱的有效消除导致了NWs光学质量的提高。因此,SCLC机制的I-V-T分析已被证明是一种获取NWs中生长诱导陷阱信息的简单方法。