Growth of Hexagonal Boron Nitrides by MOCVD and Their Applications

Hexagonal boron nitride (h-BN), an insulating two-dimensional layered material, has recently attracted a great attention due to its fascinating optical, electrical, and thermal properties, and promising applications across the fields of photonics, quantum optics, and electronics. However, mechanically exfoliated bulk h-BN and h-BN films grown on catalytic metal substrates have been mainly used to study the fundamental properties, lacking in scalability for practical implementation of h-BN. Here, we present a scalable approach for growing high-quality h-BN on various substrates, including Si and epitaxial III-Nitrides, via metal-organic chemical vapor deposition (MOCVD), and its various electronics and photonics applications.
For implementation of wafer-scale h-BN films into current state-of-the-art Si-based microelectronics technology, we demonstrate the conformal growth of sp² hybridized few-layer h-BN over an array of Si-based nanotrenches with 45 nm pitch and the aspect ratio of ~ 7:1. Surface-sensitive near-edge X-ray absorption fine structure (NEXAFS) spectroscopy and density functional theory calculations reveal that the B-O bonds formed on the non-catalytic SiO₂ surface act as nucleation sites for the formation of mixed sp²-and sp³-hybridized BON2 and BN3, facilitating the conformal growth of sp²-hybridized h-BN with excellent step coverage.
In addition, we demonstrate the scalable use of uniform h-BN van der Waals passivation layer on a 2-inch AlGaN/GaN high-electron mobility transistor (HEMT) wafer via MOCVD. The resulting HEMTs demonstrated outstanding radio-frequency (rf) performance, with f_T and f_MAX values reacing 28 and 88 GHz, respectively. Structural, spectroscopic, and theoretical analyses revealed an atomically sharp heterointerface between the h-BN layer and the AlGaN surface, underscoring the potential of h-BN for advanced device passivation. We believe that these results can provide a broad avenue for the implementation of fascinating 2D materials for current state-of-the-art microelectronics technology.
As a demonstration of an active electronic component, we fabricated an analog switching memristor using an MOCVD-grown h-BN memristive layer suspended on GaN nanocones for artificial neural network applications. Our unique h-BN on GaN nanocone heterostructure exhibits analog switching behavior with high endurance and low operation voltage. Consecutive conductive atomic force microscopy measurements reveal gradual formation of multiple nano-filaments, leading to a reduced Joule heating and a significant increase in device endurance, evidenced by a decrease in cycle-to-cycle conductance variation from 59% to 8%. This improvement enables linear and symmetric synaptic weight updates, achieving a high accuracy of 97.1% in MNIST handwritten digit recognition task simulation.
In addition to electronics applications, leveraging the unique properties of h-BN, our recent results demonstrate its potential in deep ultraviolet optoelectronics and quantum emitters. We report the development of an h-BN/GaN heterostruture photodetector, exhibiting high responsivity and selectivity in the deep ultraviolet range. Furthermore, using MOCVD, we have successfully incorporated carbon into the h-BN matrix, resulting in enhanced structural and optical properties and advancing the scalable fabrication of h-BN-based quantum devices. These advancements underscore the versatility of h-BN and provide a strategic pathway for its implementation in advanced photonic and quantum technologies.