Kang Taeho, Choi Haeju, Li Jinshu, Kang Chanwoo, Hwang Euyheon, Lee Sungjoo
SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University, Suwon, 16419, South Korea.
Department of Nano Science and Technology, Sungkyunkwan University, Suwon, 16419, South Korea.
Nano Converg. 2023 Mar 17;10(1):13. doi: 10.1186/s40580-023-00361-x.
Carrier multiplication via impact ionization in two-dimensional (2D) layered materials is a very promising process for manufacturing high-performance devices because the multiplication has been reported to overcome thermodynamic conversion limits. Given that 2D layered materials exhibit highly anisotropic transport properties, understanding the directionally-dependent multiplication process is necessary for device applications. In this study, the anisotropy of carrier multiplication in the 2D layered material, WSe, is investigated. To study the multiplication anisotropy of WSe, both lateral and vertical WSe field effect transistors (FETs) are fabricated and their electrical and transport properties are investigated. We find that the multiplication anisotropy is much bigger than the transport anisotropy, i.e., the critical electric field (E) for impact ionization of vertical WSe FETs is approximately ten times higher than that of lateral FETs. To understand the experimental results we calculate the average energy of the carriers in the proposed devices under strong electric fields by using the Monte Carlo simulation method. The calculated average energy is strongly dependent on the transport directions and we find that the critical electric field for impact ionization in vertical devices is approximately one order of magnitude larger than that of the lateral devices, consistent with experimental results. Our findings provide new strategies for the future development of low-power electric and photoelectric devices.
通过二维（2D）层状材料中的碰撞电离实现载流子倍增，对于制造高性能器件来说是一个非常有前景的过程，因为据报道这种倍增能够克服热力学转换极限。鉴于二维层状材料表现出高度各向异性的输运特性，了解方向依赖的倍增过程对于器件应用是必要的。在本研究中，对二维层状材料WSe₂中的载流子倍增各向异性进行了研究。为了研究WSe₂的倍增各向异性，制备了横向和纵向的WSe₂场效应晶体管（FET），并对其电学和输运特性进行了研究。我们发现倍增各向异性比输运各向异性大得多，即纵向WSe₂ FET碰撞电离的临界电场（E）大约是横向FET的十倍。为了理解实验结果，我们使用蒙特卡罗模拟方法计算了强电场下所提出器件中载流子的平均能量。计算出的平均能量强烈依赖于输运方向，并且我们发现纵向器件中碰撞电离的临界电场比横向器件大约大一个数量级，这与实验结果一致。我们的研究结果为低功耗电气和光电器件的未来发展提供了新策略。
