Mechanism elucidation of unusual piezoelectric relaxation of GaN caused by hopping conduction of carriers

2020 Fiscal Year Final Research Report

• Project/Area Number: 19K15450
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 29030:Applied condensed matter physics-related
• Research Institution: Iwate University
• Principal Investigator: Adachi Kanta 岩手大学, 理工学部, 助教 (50823879)
• Project Period (FY): 2019-04-01 – 2021-03-31
• Keywords: 窒化ガリウム / 圧電分極緩和 / ホッピング伝導 / 内部摩擦

Outline of Final Research Achievements

In this study, we monitored the resonance-frequency and internal-friction behaviors of GaN for various vibrational modes at high temperatures and investigated the unusual piezoelectric relaxation of GaN. Our measurements revealed that GaN shows several internal-friction peaks whose amplitude and peak temperature depend strongly on piezoelectric polarization distributions. We also found that a decrease in a resonance frequency resulting from piezoelectric relaxation occurs in stages in response to each internal-friction peak. These findings suggest that the unusual piezoelectric relaxation of GaN is attributed to the anisotropy of hopping conduction of carriers.

Free Research Field

超音波工学

Academic Significance and Societal Importance of the Research Achievements

近年、高抵抗GaNを用いた高周波・高出力・高耐熱の電子デバイスの開発が精力的に行われており、高抵抗GaNの圧電分極緩和現象はこれらのデバイスの高温域での特性に顕著な影響を及ぼす。そのため、本研究の成果は、GaN型トランジスタ内に生じるリーク電流経路の制御や、高温環境下でも性能が低下しない高耐熱GaN型弾性波フィルタの開発などにつながることが期待される。また、圧電分極緩和現象はキャリアのホッピング伝導の特性を反映するため、本研究の成果は高抵抗GaNの電気伝導特性および弾性波の伝播特性の解明にも貢献することが期待される。