High quality metal-oxide dielectrics derived from epitaxial single-crystal metal for gate stacks on 2D semiconductor

Po-Sen Mao^1,2*, Yi-Jung Hsu¹, Sheng-Zai Liu¹, Wen-Hao Chang^1,2,3

¹Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan
²Research Center for Critical Issues, Academia Sinica, Tainan 711010, Taiwan
³Research Center for Applied Sciences, Academia Sinica, Taipei 11529, Taiwan

* Presenter:Po-Sen Mao, email:flannery0123.sc11@nycu.edu.tw

The integration of an ultrathin, high-quality gate dielectric plays a pivotal role in dictating the ultimate performance and reliability of two-dimensional (2D) semiconductor transistors. Here, a non-atomic layer deposition (ALD) method for fabricating high-quality aluminum oxide (Al₂O₃) dielectric layers is proposed. The process employs an atomic-layer-style sequence of E-beam evaporation and in-situ oxidation for forming high-quality Al₂O₃ dielectric. By leveraging the van der Waals interface of TMD materials and symmetry-matched epitaxial techniques to guide crystal orientation, a large-area and single-crystal Al(111) film is grown epitaxially on the TMD surface via E-beam evaporation. A subsequent in-situ oxidation process is then employed to form an ultra-thin and high-quality Al₂O₃ film. Transmission electron microscopy (TEM) and atomic force microscopy (AFM) reveals smooth and uniform Al₂O₃/MoS₂ interfaces. The obtained Al₂O₃ layers were further integrated into metal–insulator–semiconductor–metal (MISM) structures, where current–voltage (I–V) of leakage and breakdown field measurements were conducted to evaluate the dielectric quality. Our findings provide deep insights into the mechanisms of metal epitaxy and oxidation, enabling the controlled formation of an ultra-thin and smooth oxide layer and paving the way for the scalable integration of gate stacks on 2D semiconductors.

Keywords: semiconductor devices, low-dimensional semiconductors, material growth and synthesis, electronic transport in semiconductors