Developement and application of spatio-time-resolved cathodoluminescence for wide bandgap nanostructures

2019 Fiscal Year Final Research Report

• Project/Area Number: 17H02907
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Condensed matter physics I
• Research Institution: Tohoku University
• Principal Investigator: Chichibu Shigefusa 東北大学, 多元物質科学研究所, 教授 (80266907)
• Co-Investigator(Kenkyū-buntansha): 小島 一信 東北大学, 多元物質科学研究所, 准教授 (30534250)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: 時間空間同時分解分光 / フェムト秒電子線 / 電子顕微鏡 / カソードルミネッセンス

Outline of Final Research Achievements

Spatio-time-resolved cathodoluminescence (STRCL), which uses a femtosecond-laser-driven pulsed photoelectron gun instead of the cw electron gun of spatially resolved cathodoluminescence (CL) combined with scanning electron microscopy (SEM), is an attractive tool for probing local luminescence dynamics in quantum structures and nanostructures of wide-bandgap (WBG) semiconductors. As STRCL is based on SEM, multiscale characterization of a structure with high spatial definition is possible, and the use of pulsed electron-beams allows the sub-picosecond excitation of any WBG semiconductor. In this work, we improved the spatial resolution by introducing a high efficiency photoelectron source made of Au and adding a retarding sysytem around the sample stage. Also we improved the sensitivity and temporal resolution of the detection system. Then we characterized WBG semiconductors such as AlN, AlGaN, AlInN, BN, ZnO to clarify their emission mechanisms.

Free Research Field

半導体光物性

Academic Significance and Societal Importance of the Research Achievements

サブマイクロメートル台の空間分解能とピコ秒台の時間分解能を併せ持ち、かつ光励起が困難な禁制帯幅が広い半導体物質に対しても使用できるSTRCL計測系は、新奇光デバイスを実現するための光物性研究に必須といえる。本研究で構築した、表面敏感にもできるリターディング機構付きSTRCL装置は、AlNやAlGaN混晶、h-BN等の深紫外波長領域で発光する材料やZnOをはじめとするナノ構造等の、微小領域における再結合寿命の計測を可能とする。
本装置を用いた光物性研究によって新奇発光素子用材料の発光機構の理解が進むことが期待される。