Sharma Pradeep Raj, Gautam Praveen, Afzal Amir Muhammad, Park Byoungchoo, Noh Hwayong
Department of Physics and Astronomy, Sejong University Seoul 05006 Republic of Korea
Department of Electrical and Biological Physics, Kwangwoon University Seoul 01897 Republic of Korea.
RSC Adv. 2021 May 18;11(29):17901-17909. doi: 10.1039/d1ra01231b. eCollection 2021 May 13.
Since the innovation of van der Waals heterostructures of 2D materials, the p-n junction diode, a building block of electronics and opto-electronics has been studied in various ways. To date most of them have been studied on SiO or other oxide substrates, although the oxide substrates cause significant degradation of the 2D material's intrinsic properties and device performances. Whereas using hexagonal boron nitride (h-BN) as an underlying layer to the 2D materials is known to preserve their properties. Here we have carefully analyzed the electrical and opto-electrical properties of a p-WSe/n-WS van der Waals heterojunction diode on SiO and the h-BN substrates. Besides the usual enhancement of the field-effect mobility of WSe and WS, we have achieved a significant enhancement of the diode rectification ratio and excellent photovoltaic characteristics on the h-BN substrate. We have obtained more than an order-of-magnitude enhancement of the diode rectification ratio and about two-fold increments in the overall opto-electronics behavior on the h-BN substrate compared with those on the SiO substrate. The values of self-powered photo responsivity and external quantum efficiency are 3 A/W and 588% respectively on the h-BN substrate at 10 mW cm photo-power density and 633 nm wavelength, whereas they reduce to about one-half on the SiO substrate.
自从二维材料的范德华异质结构出现以来，作为电子学和光电子学基础元件的 p-n 结二极管就受到了多方面的研究。迄今为止，大多数研究都是在 SiO₂ 或其他氧化物衬底上进行的，尽管氧化物衬底会导致二维材料的固有特性和器件性能显著退化。而使用六方氮化硼（h-BN）作为二维材料的底层已知可以保留其特性。在此，我们仔细分析了在 SiO₂ 和 h-BN 衬底上的 p-WSe₂/n-WS₂ 范德华异质结二极管的电学和光电特性。除了 WSe₂ 和 WS₂ 的场效应迁移率通常有所增强外，我们在 h-BN 衬底上实现了二极管整流比的显著提高以及优异的光伏特性。与在 SiO₂ 衬底上相比，我们在 h-BN 衬底上获得了超过一个数量级的二极管整流比增强以及整体光电子行为约两倍的提升。在 10 mW cm⁻² 的光功率密度和 633 nm 波长下，h-BN 衬底上的自供电光响应度和外量子效率值分别为 3 A/W 和 588%，而在 SiO₂ 衬底上它们降低到约一半。
