Elucidation and control of carrier recombination processes for the realization of AlGaN-based ultra-high efficiency ultraviolet light emitting devices

2020 Fiscal Year Final Research Report

• Project/Area Number: 16H02332
• Research Category: Grant-in-Aid for Scientific Research (A)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Electronic materials/Electric materials
• Research Institution: Kyoto University
• Principal Investigator: Funato Mitsuru 京都大学, 工学研究科, 准教授 (70240827)
• Co-Investigator(Kenkyū-buntansha): 川上 養一 京都大学, 工学研究科, 教授 (30214604)
• Project Period (FY): 2016-04-01 – 2021-03-31
• Keywords: 電子材料 / 結晶工学 / 紫外光源技術

Outline of Final Research Achievements

In this research, to achieve ultra-high efficiency emission in the deep ultraviolet region (wavelength: 210 to 300 nm) from a nitride semiconductor AlGaN, we elucidated and suppressed the non-radiative recombination process and enhanced the radiation recombination process. Regarding the former, it was found that the Al vacancies are the main non-radiative recombination centers in the conventional AlGaN-based quantum well. The understanding of the mechanism of introducing line defects was also advanced. Searching for crystal growth conditions and proposing new device structures led to the suppression of non-radiative recombination. Regarding the latter, we tried to control the polarization by using a novel crystal plane and demonstrated the enhancement of radiation recombination. Through these studies, we were able to raise the internal quantum efficiency, which was estimated to be about 0.1% at the start of the study, to about 50%.

Free Research Field

光電子材料

Academic Significance and Societal Importance of the Research Achievements

学術的意義の一つとして，ワイドギャップ半導体AlGaNの物性理解が進んだことを指摘することができる．例えば，点欠陥の光学特性への影響がAl組成を高めると顕著に表れることが実験的に示された．また，結晶成長に関連して，過飽和度が点欠陥形成に与える影響，格子緩和現象の解明，表面原子の吸着・脱離の制御による単分子層量子井戸の作製，新奇結晶面における輻射再結合の増強などで基礎的な知見が得られた．これらの基礎学術的な知見を通じて，発光効率を律速する要因のいくつかが解明され，社会実装に向けての大きな課題の一つである効率の改善に向けて重要な指針を示すことができた．