Optical characterizations in the sub-bandgap energy region of nitride semiconductor alloy thin films for the development of low-internal-loss LD waveguides

2021 Fiscal Year Final Research Report

• Project/Area Number: 20K15182
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 30010:Crystal engineering-related
• Research Institution: Meijo University
• Principal Investigator: Imai Daichi 名城大学, 理工学部, 准教授 (20739057)
• Project Period (FY): 2020-04-01 – 2022-03-31
• Keywords: 窒化物半導体 / 面発光レーザー / AlInN / サブギャップ / 光熱偏向分光法 / 分光エリプソメトリー

Outline of Final Research Achievements

In this work, we have analyzed below-bandgap optical absorption processes in AlInN thin films, which may lead to internal absorption losses of nitride-based laser diodes and/or VCSELs. Optical constants near the band-edge region and bandgap energies were analyzed by spectroscopic ellipsometry (SE). Sub-bandgap optical absorption processes were observed and analyzed by photothermal deflection spectroscopy (PDS). In SE analyses, we have proposed suitable model-dielectric-functions for AlInN alloys. Sub-bandgap optical absorption processes of AlInN thin films were successfully observed and analyzed by the PDS. It was also revealed that, by combining the SE and PDS measurements, absorption coefficients in sub-bandgap energy region of AlInN thin films could be estimated.

Free Research Field

半導体工学

Academic Significance and Societal Importance of the Research Achievements

本研究の学術的意義は、素子レベルに高品質な窒化物系混晶半導体薄膜において、サブギャップ領域の微小な光吸収過程とそれを引き起こす起源の解析、さらには吸収係数の定量評価に向けた基盤技術が構築されたことである。将来的には、窒化物系端面発光半導体レーザー(LD)や面発光レーザー(VCSEL)を構成する混晶半導体において、レーザー駆動時に損失を引き起こすサブギャップ領域の物性制御指針を、実験解析に基づき具体的に提示することが可能となると考えている。これにより窒化物系LDやVCSELの高効率・高出力化や動作波長域の拡大による省エネルギーな次世代光素子開発に貢献したい。