Development of combinational evaluation of photoemission and photoluminescence spectroscopy towards highly efficient nitride semiconductor-based optical devices

2023 Fiscal Year Final Research Report

• Project/Area Number: 22K14614
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 30010:Crystal engineering-related
• Research Institution: Osaka University
• Principal Investigator: Ichikawa Shuhei 大阪大学, 大学院工学研究科, 准教授 (50803673)
• Project Period (FY): 2022-04-01 – 2024-03-31
• Keywords: 二光子光電子分光 / 表面再結合 / 窒化物半導体

Outline of Final Research Achievements

In this research project, we directly evaluated surface carrier lifetime of InGaN, which has been extensively studied as a visible light-emitting devices, using two-photon photoemission spectroscopy.
The surface carrier lifetime on the as-grown (0001) InGaN was estimated to be 3.8 ns, which was about two orders of magnitude longer than the lifetime on a GaAs(110) surface. It indicates that the surface recombination rate of InGaN surface is significantly slower. When Cs was adsorbed on the InGaN (0001) surface to suppress surface band bending, the surface carrier lifetime was drastically reduced to 48 ps. We found that the surface recombination of InGaN is extremely dependent on the amount of surface band bending, and control of the band bending is a key technology towards highly efficient micro-sized InGaN-based optical devices.

Free Research Field

半導体光物性

Academic Significance and Societal Importance of the Research Achievements

超小型・高精細な「マイクロLEDディスプレイ」の実現にむけて、窒化物半導体光デバイスに期待が寄せられている。これまで、素子の微細化に伴って生じる非発光過程である、表面再結合過程の評価が十分でなかったが、表面敏感な二光子光電子分光法と従来の発光分光測定を組み合わせることにより、表面キャリア寿命の直接評価が可能であることを示した。異材料への適用も可能な評価手法の開発という観点から、学術的意義の高い結果が得られた。また、従来のGaAs系材料に比べると、表面再結合の影響が小さいことが示唆され、マイクロLED高効率化に向けた窒化物半導体開発の指針を得た点では、社会的な意義も高い成果となったと考える。