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Chief Scientist Laboratories Quantum Optodevice Laboratory

Chief Scientist: Hideki Hirayama (D.Eng.)

Research Summary

Hideki  Hirayama(D.Eng.)

The development of new-frequency semiconductor light sources, such as deep-ultraviolet (DUV) light-emitting diodes (LEDs) and laser diodes (LDs) or terahertz quantum-cascade lasers (THz-QCLs) is one of the most important subjects, because they are strongly required for a wide variety of potential applications, e.g. sterilization, water and air purification, medicine and biochemistry, light sources for high density optical recording, white light illumination and non-destructive see-through examinations. The Quantum Optodevice Laboratory's research is at the forefront of optics and nanotechnology, e.g. in creating innovative optical devices, including undeveloped frequency semiconductor emitters, and in developing a new research field through merging advanced optical/laser science, atomic/nano-scale material fabrication technology, novel semiconductor crystal growth technologies, and so forth. Through the introduction of novel crystal growth technology for wide-gap semiconductors, we have achieved innovative emitting devices such as highly efficient DUV-LEDs with the shortest wavelength regime (220-350nm), or THz-QCLs. We have also investigated the performance limits of these devices by introducing innovative quantum heterostructures and/or photonic nano-structures. Through the creation of the applicable field of these new emitting devices, we aim to contribute to the realization of a richer human society.

Main Research Fields

  • Engineering

Related Research Fields

  • Interdisciplinary Science & Engineering
  • Electron device, Electronic equipment
  • Optical engineering, Photon science


  • DUV-LEDs
  • Nitride Semiconductors
  • Quantum cascade laser
  • Crystal growth
  • Inter-subband transition

Selected Publications

  • 1. M. A. Khan, N. Maeda, H. Rangaraju, M. Jo, K. Iimura, and H. Hirayama.:
    "Efficiency droop in AlGaN crystal-based UVB LEDs in the context of electron blocking mechanism"
    Journal of Crystal Growth, Vol. 604, p. 127032, (2023).
  • 2. M. A. Khan, N. Maeda, Y. Itokazu, M. Jo, K. Iimura, and H. Hirayama.:
    "Milliwatt Power AlGaN Deep-UV Light-Emitting Diodes at 254 nm Emission as a Clean Alternative to Mercury Deep-UV Lamps"
    physica status solidi (a), Vol. 220, No. 1, p. 2200621, (2023).
  • 3. Y. Itokazu, N. Maeda, H. Yaguchi, and H. Hirayama.:
    "Significant improvement of injection efficiency in deep-UV LD structures by light Mg doping in p-core layer"
    Japanese Journal of Applied Physics, Vol. 62, p. SC1091, (2023).
  • 4. K. Nagamatsu, T. Miyagawa, A. Tomita, H. Hirayama, Y. Takashima, and Y. Naoi.:
    "High growth temperature for AlN by jet stream gas flow metalorganic vapor phase epitaxy"
    Scientific Reports, Vol. 13, No. 1, p. 2438, (2023).
  • 5. M. A. Khan, Y. Itokazu, N. Maeda, M. Jo and H. Hirayama.:
    "Realization of high injection current density up to 200 kA/cm-2 in electrically pumped AlGaN ultraviolet laser diodes on c-sapphire substrate"
    Optical Materials, 133, 112927, (2022).
  • 6. M. A. Khan, N. Maeda, J. Yun, M. Jo, Y. Yamada, and H. Hirayama.:
    "Achieving 9.6% Efficiency in 304 nm p-AlGaN UVB LED via Increasing the Holes Injection and Light Reflectance"
    Scientific Reports 12 (1), 1-11, (2022).
  • 7. M. A. Khan, N. Maeda, M. Jo, Y. Yamada, and H. Hirayama.:
    "Highly Transparent p-AlGaN-Based (326-341 nm)-Band Ultraviolet-A Light-Emitting Diodes on AlN Templates: Recent Advances and Perspectives"
    Physica Status Solidi A, Vol. 219, No. 7, p. 2100605, (2022).
  • 8. H. Murotani, Y. Yamada, and H. Hirayama.:
    "Excitonic optical properties of deep-UV luminescent AlGaN"
    JSAP Review, 220405, September 1, (2022). 10.11470/jsaprev.220405
  • 9. S. Tsuda, T. Miyagawa, R. Aono, H. Hirayama, Y. Takashima, and Y. Naoi.:
    "Reduction of parasitic reaction in high-temperature AlN growth by jet stream gas flow metal-organic vapor phase epitaxy"
    Scientific Reports 12 (1), 1-7, (2022).

Recent Research Results

Annual research report

Related Links

Lab Members

Principal investigator

Hideki Hirayama
Chief Scientist

Core members

Muhammad Ajmal Khan
Research Scientist
Yukio Kashima
Technical Staff II
Eriko Matsuura
Visiting Technician
Noritoshi Maeda
Research Consultant

Contact Information

Cooperation Center, W514
2-1 Hirosawa, Wako, Saitama 351-0198, Japan
Tel: +81-(0)48-467-9387
Fax: +81-(0)48-462-4647
Email: hirayama [at] riken.jp