Self-Aligned van der Waals Heterojunction Diodes and Transistors

TL;DR

This paper introduces a versatile self-aligned fabrication method for van der Waals heterojunction devices, enabling high-performance transistors and diodes with nanoscale precision and scalability for advanced electronic applications.

Contribution

It presents a general self-aligned fabrication scheme for van der Waals heterojunction devices, including transistors and diodes, with demonstrated scalability and design insights.

Findings

Achieved near-ideal current saturation in monolayer MoS2 transistors.

Demonstrated gate-tunable anti-ambipolar characteristics in heterojunction diodes.

Fabricated sub-200 nm channel length transistors on large-area CVD-grown MoS2.

Abstract

A general self-aligned fabrication scheme is reported here for a diverse class of electronic devices based on van der Waals materials and heterojunctions. In particular, self-alignment enables the fabrication of source-gated transistors in monolayer MoS2 with near-ideal current saturation characteristics and channel lengths down to 135 nm. Furthermore, self-alignment of van der Waals p-n heterojunction diodes achieves complete electrostatic control of both the p-type and n-type constituent semiconductors in a dual-gated geometry, resulting in gate-tunable mean and variance of anti-ambipolar Gaussian characteristics. Through finite-element device simulations, the operating principles of source-gated transistors and dual-gated anti-ambipolar devices are elucidated, thus providing design rules for additional devices that employ self-aligned geometries. For example, the versatility of this scheme is demonstrated via contact-doped MoS2 homojunction diodes and mixed-dimensional heterojunctions based on organic semiconductors. The scalability of this approach is also shown by fabricating self-aligned short-channel transistors with sub-diffraction channel lengths in the range of 150 nm to 800 nm using photolithography on large-area MoS2 films grown by chemical vapor deposition. Overall, this self-aligned fabrication method represents an important step towards the scalable integration of van der Waals heterojunction devices into more sophisticated circuits and systems.