Hysteresis-Free Contact Doping for High-Performance Two-Dimensional Electronics

Abstract

Contact doping is considered crucial for reducing the contact resistance of two-dimensional (2D) transistors. However, a process for achieving robust contact doping for 2D electronics is lacking. Here, we developed a two-step doping method for effectively doping 2D materials through a defect-repairing process. The method achieves strong and hysteresis-free doping and is suitable for use with the most widely used transition-metal dichalcogenides. Through our method, we achieved a record-high sheet conductance (0.16 mS·sq–1 without gating) of monolayer MoS2 and a high mobility and carrier concentration (4.1 × 1013 cm–2). We employed our robust method for the successful contact doping of a monolayer MoS2 Au-contact device, obtaining a contact resistance as low as 1.2 kΩ·μm. Our method represents an effective means of fabricating high-performance 2D transistors.

High-Performance Contact-Doped WSe2 Transistors Using TaSe2 Electrodes

“…Chemical doping , and O 2 plasma/O 3 , have been used for contact doping for 2D electronic devices, but these methods may lead to device instabilities and degradation of doping. Laser has been demonstrated as a versatile tool to dope the 2D materials − and modify their properties. − Laser doping is an effective method to generate dopants through inducing oxidation on the surface, resulting in charge transfer at the interface. − In addition, laser doping offers area selectivity, , which avoids the undesired contaminations caused by the multistep process of other lithography-assisted doping methods. , Another approach is to select a metal contact with appropriate work function to decrease the Schottky barrier height (SBH) . However, this method is restricted due to Fermi level pinning with bulk metal materials. , 2D metallic materials, such as graphene or metallic TMDs, appear to be more promising than conventional metals. , Seamless edge contact can be formed between 2D metallic contacts and 2D TMDs, preventing atomically sharp discontinuity and chemical disorder caused by interfaces between 2D TMDs and bulk metals, leading to unpin the Fermi level and lower the SBH. , Contact doping and 2D metallic materials were individually applied to optimize the R c of TMD-based FETs.…”

“…34−36 In addition, laser doping offers area selectivity, 37,38 which avoids the undesired contaminations caused by the multistep process of other lithography-assisted doping methods. 39,40 Another approach is to select a metal contact with appropriate work function to decrease the Schottky barrier height (SBH). 41 However, this method is restricted due to Fermi level pinning with bulk metal materials.…”

High-Performance WSe2 Top-Gate Devices with Strong Spacer Doping

“…Most underlap top-gate devices contain a global back gate that simply helps them exhibit extraordinary dual-gate performance but cannot be truly applied in the circuits due to the presence of intolerable parasitic capacitance. Therefore, doping in the contact and spacer regions is the key for pursuing high-performance 2D devices. , Various types of doping techniques have been developed for transistor production, and three types of doping methods are generally used: substitutional, − covalently functionalized, ,− and surface charge transfer − doping. The substitutional doping is the most stable technique because chemical bonding occurs between dopants and semiconductors in this method.…”