MoS₂/Si tunnel diodes based on comprehensive transfer technique

Abstract

Due to the pristine interface of the 2D/3D face-tunneling heterostructure with an ultra-sharp doping profile, the 2D/3D TFET is considered as one of the most promising low-power devices that can simultaneously obtain low OFF-state current (I OFF), high ON-state current (I ON) and steep subthreshold swing (SS). As a key element for the 2D/3D TFET, the intensive exploration of the tunnel diode based on the 2D/3D heterostructure is in urgent need. The transfer technique composed of the exfoliation and the release process is currently the most common approach to fabricating the 2D/3D heterostructures. However, the well-established transfer technique of the 2D materials is still unavailable. Only a small part of the irregular films can usually be obtained by mechanical exfoliation, while the choice of the chemical exfoliation may lead to the contamination of the 2D material films by the ions in the chemical etchants. Moreover, the deformation of the 2D material in the transfer process due to its soft nature also leads to the nonuniformity of the transferred film, which is one of the main reasons for the presence of the wrinkles and the stacks in the transferred film. Thus, the large-scale fabrication of the high-quality 2D/3D tunnel diodes is limited. In this article, a comprehensive transfer technique that can mend up the shortages mentioned above with the aid of the water and the thermal release tape (TRT) is proposed. Based on the method we proposed, the MoS2/Si tunnel diode is experimentally demonstrated and the transferred monolayer MoS2 film with the relatively high crystal quality is confirmed by AFM, SEM, and Raman characterizations. Besides, the prominent NDR effect is observed at room temperature, which verifies the relatively high quality of the MoS2/Si heterojunction. The bilayer MoS2/Si tunnel diode is also experimentally fabricated by repeating the transfer process we proposed, followed by the specific analysis of the electrical characteristics. This study shows the advantages of the transfer technique we proposed and indicates the great application foreground of the fabricated 2D/3D heterostructure for ultralow-power tunneling devices.