Electrical Properties of N‐Polar GaN/AlGaN/AlN Grown via Metal‐Organic Vapor Phase Epitaxy

• Published in: Physica status solidi. A, Applications and materials science Applications and materials science, 2024-11, Vol.221 (21), p.n/a
• Main Authors: Zazuli, Aina Hiyama, Kowaki, Taketo, Miyamoto, Minagi, Hanasaku, Koki, Inahara, Daisuke, Fujii, Kai, Kurai, Satoshi, Okada, Narihito, Yamada, Yoichi
• Format: Article
• Language: English
• Subjects: Aluminum gallium nitrides; Aluminum nitride; Electrical properties; Electron gas; Electron mobility; Epitaxial growth; field‐effect transistors; Gallium nitrides; Heterostructures; Metalorganic chemical vapor deposition; metal‐organic vapor phase epitaxies (MOVPEs); mobilities; Morphology; N‐polar GaN; Sapphire; Transistors; Vapor phase epitaxy; Vapor phases
• ISSN: 1862-6300; 1862-6319
• DOI: 10.1002/pssa.202400060

The metal‐organic vapor phase epitaxy (MOVPE) method faces several challenges when used for the growth of N‐polar GaN on foreign substrates, including the presence of a rough surface morphology characterized by step bunching or hexagonal hillocks. In this study, it is aimed to address these issues by establishing optimal growth conditions for the MOVPE method, enabling the growth of N‐polar GaN/Al0.9Ga0.1N/AlN heterostructures with a smooth surface morphology on a vicinal sapphire substrate. The formation of 2D electron gas (2DEG) in N‐polar GaN/AlGaN/AlN prepared using MOVPE is discussed. Additionally, in the study, the impact of growth conditions, such as temperature and V/III ratio, on the electrical properties of N‐polar GaN is investigated. In the results, it is revealed that growth at lower temperatures and a V/III ratio of 30 000 effectively suppresses 3D growth. Moreover, an increase in the V/III ratio correlates with a decrease in residual impurity concentrations (C and H); hence, electron mobility improves. Moreover, the N‐polar GaN/AlGaN/AlN field‐effect transistor, grown under optimized conditions, exhibits a higher maximum drain–source current (IDmax). In these results, possibilities are broadened for the high performance of N‐polar GaN channel high‐electron‐mobility transistors through MOVPE. N‐polar GaN growth on AlN by metal‐organic vapor phase epitaxy (MOVPE) has succeeded under low growth temperatures and high V/III ratios. The 2D electron gas formation is confirmed by temperature‐dependent carrier mobilities and concentrations. The field‐effect transistor fabricated using the MOVPE‐grown substrate exhibits an maximum drain current of 139.3 mA mm−1.