Yoon Minho
Department of Physics and Institute of Quantum Convergence Technology, Kangwon National University, Chuncheon 24341, Republic of Korea.
Materials (Basel). 2023 Apr 7;16(8):2940. doi: 10.3390/ma16082940.
In this paper, we present a threshold-voltage extraction method for zinc oxide (ZnO) thin-film transistors (TFTs). Bottom-gate atomic-layer-deposited ZnO TFTs exhibit typical n-type enhancement-mode transfer characteristics but a gate-voltage-dependent, unreliable threshold voltage. We posit that this obscure threshold voltage is attributed to the localized trap states of ZnO TFTs, of which the field-effect mobility can be expressed as a gate-bias-dependent power law. Hence, we derived the current-voltage relationship by dividing the drain current with the transconductance to rule out the gate-bias-dependent factors and successfully extract the reliable threshold voltage. Furthermore, we investigated the temperature-dependent characteristics of the ZnO TFTs to validate that the observed threshold voltage was genuine. Notably, the required activation energies from the low-temperature measurements displayed an abrupt decrease at the threshold voltage, which was attributed to the conduction route change from diffusion to drift. Thus, we conclude that the reliable threshold voltage of accumulation-mode ZnO TFTs can be determined using a gate-bias-dependent factor-removed current-voltage relationship with a low-temperature analysis.
在本文中，我们提出了一种用于氧化锌（ZnO）薄膜晶体管（TFT）的阈值电压提取方法。底部栅极原子层沉积的ZnO TFT表现出典型的n型增强模式转移特性，但阈值电压与栅极电压有关且不可靠。我们认为这种模糊的阈值电压归因于ZnO TFT的局部陷阱态，其场效应迁移率可以表示为与栅极偏置相关的幂律。因此，我们通过将漏极电流除以跨导来推导电流 - 电压关系，以排除与栅极偏置相关的因素，并成功提取了可靠的阈值电压。此外，我们研究了ZnO TFT的温度依赖性特性，以验证观察到的阈值电压是真实的。值得注意的是，低温测量所需的激活能量在阈值电压处显示出突然下降，这归因于传导途径从扩散到漂移的变化。因此，我们得出结论，通过使用与栅极偏置相关的因素去除电流 - 电压关系并进行低温分析，可以确定累积模式ZnO TFT的可靠阈值电压。
