Creation of early transition metal-based semiconductors for high efficiency LED utilizing non-bonding crystal orbital

2022 Fiscal Year Final Research Report

• Project/Area Number: 20H02434
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 26020:Inorganic materials and properties-related
• Research Institution: National Institute for Materials Science (2021-2022); Tokyo Institute of Technology (2020)
• Principal Investigator: Iimura Soshi 国立研究開発法人物質・材料研究機構, 機能性材料研究拠点, 主任研究員 (80717934)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: 半導体 / 電子構造 / 発光 / 結晶軌道

Outline of Final Research Achievements

Semiconductors for LED need to possess appropriate band-edge energy that can stabilize n- and p-type carriers and strong band-edge optical absorption coefficient. The purpose of this research is to design such semiconductors by forcusing on the chemical bonding states of the crystal orbitals and clarify the physical properties. In this research, it is found that 1) early transition metal hydride, LaH3, have a very shallow valence band composed by hydrogen 1s2 orbital appropriate for p-type doping and 2) Indium halide with a shallow s-orbital valence band similar to that of LaH3 shows strong optical absorption coefficient at band edge and orrange-colored band edge emission.

Free Research Field

半導体

Academic Significance and Societal Importance of the Research Achievements

前周期遷移金属化合物はポスト遷移金属とは異なり、価電子帯に寄与する充填d軌道やs軌道を持たないため、p型化が難しい。しかし本研究を通して、水素の陰イオンが持つ充填s軌道はp型キャリアを安定化できるほどに浅い価電子帯（真空準位基準で-4eVほど）を作ることが明らかになった。また、s軌道同士の大きな重なりのためにH-1s2から成る価電子帯はバンド幅も広く、有効質量もポスト遷移金属化合物と同等に軽かった(m*~1)。本成果はこれまで銅や錫、鉛などの化合物に限られてきたp型半導体材料の幅を大きく拡張し、無毒で環境調和性の高い半導体発光デバイス創製に向けた新たなアプローチを提供するものである。