Development of infrared photothermal deflection spectroscopy suitable for defect level evaluation of phase-change memory and selector materials

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K04861
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 29010:Applied physical properties-related
• Research Institution: Gunma University
• Principal Investigator: Gotoh Tamihiro 群馬大学, 大学院理工学府, 教授 (10311523)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: 光熱偏向分光法 / アモルファス半導体 / 局在準位 / 相変化メモリ / 電気スイッチ / カルコゲナイド / 赤外線 / 状態密度

Outline of Final Research Achievements

Chalcogenide semiconductors are expected to be applied to nonvolatile memories. In order to improve the performance and reliability of devices, localized level information related to carrier characteristics is essential. Therefore, an infrared photothermal deflection spectroscopy method suitable for phase change memory selector materials was developed, and the localized levels of these materials were evaluated.
A photothermal deflection spectroscopy system using excitation light with a wavelength of up to 5000 nm (light energy 0.25 eV) in the infrared region has been developed. By using sapphire as a substrate, which is transparent in a wide wavelength range including infrared, it became possible to quantify low-density defects and impurities in amorphous chalcogenide films.

Free Research Field

半導体物性

Academic Significance and Societal Importance of the Research Achievements

赤外線領域まで拡張し、高感度化した光熱偏向分光システムは世界的に報告例が無く、新規性が高い。一方、相変化メモリ・セレクタにおいて、デバイス動作時の抵抗遷移過程を理解し、高性能化・信頼性向上を実現するには、キャリア特性に関与する局在準位情報が必要不可欠である。独自に開発した赤外光熱偏向分光法を用い、カルコゲナイド半導体薄膜の欠陥吸収を測定し、局在準位を含む状態密度を求める学術的意義は大きい。また、相変化メモリ・セレクタ等のデバイス開発を基礎科学から支える社会的意義を有している。