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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.Takano, T., Mino, T., Sakai, J., Noguchi, and Hirayama, H.:
    "Deep-ultraviolet light-emitting diodes with external quantum efficiency higher than 20% at 275 nm achieved by improving light-extraction efficiency"
    Applied Physics Express, Vol. 10, No. 3, pp. 031002-1-4 (2017).
  • 2.Yun, J. and Hirayama, H.:
    "Investigation of the light-extraction efficiency in 280 nm AlGaN-based light-emitting diodes having a highly transparent p-AlGaN contact layer"
    Journal of Applied Physics, Vol. 121, No. 1, 013105-1-9 (2017).
  • 3.Jo, M., Oshima, I., Matsumoto, T., Maeda, N., Kamata, N. and Hirayama, H:
    "Structural and electrical properties of semipolar (11‐22) AlGaN grown on m‐plane (1‐100) sapphire substrates"
    physica status solidi c, Vol. 14, No. 8, pp. 1600248-1-3 (2017).
  • 4.Tran, B. T., Hirayama, H., Jo, M., Maeda, N., Inoue, D. and Kikitsu, T.:
    "High-quality AlN template grown on a patterned Si (111) substrate"
    Journal of Crystal Growth, Vol. 468, No. 15, pp. 225-229 (2017).
  • 5.Tran, B. T., Maeda, N., Jo, M., Inoue, D., Kikitsu, T. and Hirayama, H:
    "Performance improvement of AlN crystal quality grown on patterned Si (111) substrate for deep UV-LED applications"
    Scientific Reports, Vol. 6, Article number. 35681 (2016).
  • 6.Jo, M., Maeda, N. and Hirayama, H:
    "Enhancement of light extraction efficiency in 260 nm light-emitting diode with a highly transparent p-AlGaN layer"
    App. Phys. Express, Vol. 9, No. 1, p. 01202-1-3 (2016).
  • 7.Tran, B. T., Hirayama, H., Maeda, N., Jo, M., Toyoda, S. and Kamata, N.:
    "Direct growth and controlled coalescence of thick AlN template on micro-circle patterned Si substrate"
    Scientific Report, Vol. 5, pp. 14734 (2015).
  • 8.Yun, J., Shim, J. I. and Hirayama, H.:
    "Analysis of efficiency droop in 280 nm AlGaN multiple-quantum-well light-emitting diodes based on carrier rate equation"
    Appl. Phys. Express, Vol. 8, No. 2, pp. 022104-1-3 (2015).
  • 9.Hirayama, H., Maeda, N., Fujikawa, S., Toyoda, S. and Kamata, N.:
    "Recent progress and future prospects of AlGaN-based high-efficiency deep-ultraviolet light-emitting diodes"
    Jap. J. Appl. Phys. (Selected Topic), Vol. 53, No. 10, pp. 100209 1-10 (2014).
  • 10.Lin, T. T. and Hirayama, H.:
    "Improvement of operation temerature in GaAs/AlGaAs THz-QCLs by utilizing high Al conposition barrier"
    Phys. Status Solidi (c), Vol. 10, No. 11, pp. 1430-1433 (2013).

Recent Research Results

Annual research report

Lab Members

Principal investigator

Hideki Hirayama
Chief Scientist

Core members

Noritoshi Maeda
Research Scientist
Yukio Kashima
Technical Staff II
Eriko Matsuura
Visiting Technician

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