Dhara Soumen, Niang Kham M, Flewitt Andrew J, Nathan Arokia, Lynch Stephen A
School of Physics and Astronomy, Cardiff University, Cardiff, CF24 3AA, UK.
Faculty of Science, Sri Sri University, Cuttack, 754006, India.
Sci Rep. 2021 Sep 24;11(1):19016. doi: 10.1038/s41598-021-98339-4.
We report on the appearance of a strong persistent photoconductivity (PPC) and conductor-like behaviour in zinc tin oxide (ZTO) thinfilm phototransistors. The active ZTO channel layer was prepared by remote plasma reactive sputtering and possesses an amorphous structure. Under sub-bandgap excitation of ZTO with UV light, the photocurrent reaches as high as ~ 10 A (a photo-to-dark current ratio of ~ 10) and remains close to this high value after switching off the light. During this time, the ZTO TFT exhibits strong PPC with long-lasting recovery time, which leads the appearance of the conductor-like behaviour in ZTO semiconductor. In the present case, the conductivity changes over six orders of magnitude, from ~ 10 to 0.92/Ω/cm. After UV exposure, the ZTO compound can potentially remain in the conducting state for up to a month. The underlying physics of the observed PPC effect is investigated by studying defects (deep states and tail states) by employing a discharge current analysis (DCA) technique. Findings from the DCA study reveal direct evidence for the involvement of sub-bandgap tail states of the ZTO in the strong PPC, while deep states contribute to mild PPC.
我们报道了氧化锌锡（ZTO）薄膜光电晶体管中出现的强持久光电导（PPC）和类似导体的行为。活性ZTO沟道层通过远程等离子体反应溅射制备，具有非晶结构。在紫外光对ZTO进行亚带隙激发时，光电流高达约10 A（光暗电流比约为10），关灯后仍接近这一高值。在此期间，ZTO薄膜晶体管表现出具有长恢复时间的强PPC，这导致ZTO半导体中出现类似导体的行为。在当前情况下，电导率变化超过六个数量级，从约10到0.92/Ω/cm。紫外光照射后，ZTO化合物可能在导电状态下保持长达一个月。通过采用放电电流分析（DCA）技术研究缺陷（深能级和尾态），对观察到的PPC效应的潜在物理机制进行了研究。DCA研究结果揭示了ZTO的亚带隙尾态参与强PPC的直接证据，而深能级则导致轻微的PPC。
