Single-Crystalline III-N Film Growth for Photonic, Electronic, Sensing, and Energy Harvesting Applications



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The flexible platform will be the next generation of electronic devices for the growing demand of the industry. Current flexible devices are made by the deposition of non-single-crystal thin films on flexible substrates or by the layer transfer of single-crystal thin films onto secondary flexible substrates, which result in low performance devices or complicated fabrication processes, respectively. We develop a process for direct deposition of single-crystal-like semiconductor films on flexible substrates to achieve high-performance flexible devices using simple fabrication process. For the transfer-free direct deposition of flexible III-N films, we demonstrated high-crystalline-quality aluminum nitride (AlN) and gallium nitride (GaN) on a flexible copper (Cu) foil/tape using graphene as an intermediate seed layer. Graphene and AlN were directly grown by chemical vapor deposition and DC reactive magnetron sputtering, respectively, to achieve a highly-textured AlN film in both a- and c-crystallographic directions. Then, single-crystal-like GaN layer was grown by metalorganic chemical vapor deposition (MOCVD) on the AlN buffer layer. The proposed method enables continuous roll-to-roll process for device fabrication, bringing economic advantages to the semiconductor technology with low-cost and large-scale manufacturing capability. In addition, group IIIa-N materials, such as AlN and GaN thin films, draw increasing attention in piezoelectric applications due to their exceptional properties of high-temperature stability, spontaneous electric polarization, low dielectric permittivity, high sound velocity, efficient transduction, and high stiffness. However, the piezoelectric coefficients and the resulting electromechanical coupling factors (kt2) of III-N materials are relatively low as compared to those of currently dominant piezoelectric materials such as lead zirconate titanate. Transition-metal-alloyed III-V nitride thin films cause significant impact on the enhancement of the piezoelectric properties in group-IIIa-N (III-N) films, such as wurtzite AlN, by group-IIIb transition metals. Therefore, we focus on a new Hybrid Chemical Vapor (HybCVD) thin film growth method along with theoretically study the thermodynamics of (1) precursor reaction chemistry and (2) solid-phase formation of ScAlN, YGaN and YAlN in different parts of source zones and mixing/growth zone. The combination of MOCVD and HVPE growth methods simultaneously provides well control on the uniformity and quality of piezoelectric films based on transition-metal-alloyed III-N materials.



III-N materials, HybCVD, Thin films, Flexible devices, Piezoelectric, Thermodynamics


Portions of this document appear in: Moradnia, M.; Pouladi, S.; Chen, J.; Kim, N.-I.; Aigbe, O.; Ryou, J.-H. Thermodynamic Analysis of Hybrid Chemical Vapor Deposition of Transition-Metal-Alloyed Group-III-Nitride ScAlN Piezoelectric Semiconductor Films. Cryst. Growth Des. 2021, 22, 2239–2247.; and in: Shervin, S.; Moradnia, M.; Alam, M. K.; Tong, T.; Ji, M. H.; Chen, J.; Pouladi, S.; Detchprohm, T.; Forrest, R.; Bao, J.; Dupuis, R. D.; Ryou, J. H. Flexible Single-Crystalline GaN Substrate by Direct Deposition of III-N Thin Films on Polycrystalline Metal Tape. J. Mater. Chem. C 2021, 9 (7), 2243–2251.; and in: Moradnia, M.; Pouladi, S.; Aqib, M.; Ryou, J. H. Thermodynamic Analysis of Group-III-Nitride Alloying with Yttrium by Hybrid Chemical Vapor Deposition. Nanomaterials 2022, 12 (22).