Department of Energy Science, Sungkyunkwan University (SKKU) , Suwon 16419, Korea.
Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS) , Suwon 16419, Republic of Korea.
ACS Appl Mater Interfaces. 2016 Jul 27;8(29):19092-9. doi: 10.1021/acsami.6b02085. Epub 2016 Jul 15.
For transition metal dichalcogenides, the fluctuation of the channel current due to charged impurities is attributed to a large surface area and a thickness of a few nanometers. To investigate current variance at the interface of transistors, we obtain the low-frequency (LF) noise features of MoTe2 multilayer field-effect transistors with different dielectric environments. The LF noise properties are analyzed using the combined carrier mobility and carrier number fluctuation model which is additionally parametrized with an interfacial Coulomb-scattering parameter (α) that varies as a function of the accumulated carrier density (Nacc) and the location of the active channel layer of MoTe2. Our model shows good agreement with the current power spectral density (PSD) of MoTe2 devices from a low to high current range and indicates that the parameter α exhibits a stronger dependence on Nacc with an exponent -γ of -1.18 to approximately -1.64 for MoTe2 devices, compared with -0.5 for Si devices. The raised Coulomb scattering of the carriers, particularly for a low-current regime, is considered to be caused by the unique traits of layered semiconductors such as interlayer coupling and the charge distribution strongly affected by the device structure under a gate bias, which completely change the charge screening effect in MoTe2 multilayer. Comprehensive static and LF noise analyses of MoTe2 devices with our combined model reveal that a chemical-vapor deposited h-BN monolayer underneath MoTe2 channel and the Al2O3 passivation layer have a dissimilar contribution to the reduction of current fluctuation. The three-fold enhanced carrier mobility due to the h-BN is from the weakened carrier scattering at the gate dielectric interface and the additional 30% increase in carrier mobility by Al2O3 passivation is due to the reduced interface traps.
对于过渡金属二卤化物，由于带电杂质引起的沟道电流波动归因于较大的表面积和几纳米的厚度。为了研究晶体管界面的电流变化，我们获得了具有不同介电环境的 MoTe2 多层场效应晶体管的低频（LF）噪声特性。使用组合载流子迁移率和载流子数波动模型分析 LF 噪声特性，该模型还参数化了一个界面库仑散射参数（α），该参数随积累载流子密度（Nacc）和 MoTe2 的有源沟道层的位置而变化。我们的模型很好地符合了从低电流到高电流范围的 MoTe2 器件的电流功率谱密度（PSD），并表明参数α对 Nacc 的依赖性更强，对于 MoTe2 器件，其指数为-1.18 至约-1.64，而 Si 器件为-0.5。载流子的库仑散射增强，特别是在低电流区域，被认为是由层状半导体的独特特性引起的，例如层间耦合和电荷分布强烈受到栅极偏置下器件结构的影响，这完全改变了 MoTe2 多层中的电荷屏蔽效应。使用我们的组合模型对 MoTe2 器件进行综合静态和 LF 噪声分析表明，MoTe2 沟道下方的化学气相沉积 h-BN 单层和 Al2O3 钝化层对降低电流波动有不同的贡献。由于 h-BN 导致的载流子迁移率提高了三倍，这是由于栅介质界面处的载流子散射减弱，而 Al2O3 钝化导致的载流子迁移率额外提高了 30%，这是由于界面陷阱减少。
