Hybrid Integration of n-MoS₂/p-GaN Diodes by Quasi-van der Waals Epitaxy

Compound semiconductor heterojunctions have enabled various optoelectronic devices. Nonetheless, the formation of heterojunctions is limited by the lattice matching between the two materials. On the other hand, two-dimensional (2D) semiconducting material and three-dimensional (3D) material heterojunction has attracted tremendous attention in recent years due to its immunity to the lattice mismatch. However, 2D/3D heterojunction formation by transferring 2D material suffers from contamination and defects created during the transfer process. Thus, direct growth of 2D material on 3D semiconducting material is crucial for the next generation heterojunction devices. In this work, we demonstrate n-MoS2/p-GaN diodes monolithically formed by quasi-van der Waals epitaxy. Monolayer MoS2 has been grown on a GaN substrate through a powder-based chemical vapor deposition (CVD) system. The triangular MoS2 flakes show well-aligned morphology with the GaN hexagonal crystal structure in the initial stage of the growth. Raman and PL mapping confirms the excellent uniformity of the monolayer MoS2 film on the GaN substrate. The growth of MoS2 on patterned GaN substrates are also studied, which yields monolayer and few-layer MoS2 formation on the planar surface and the pyramidal sidewalls, respectively. Finally, the n-MoS2/p-GaN diodes have been electrically characterized and show well-defined rectifying behavior with an ideality factor of ∼1.3.