Quantum Optodevice Laboratory

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.

Research Subjects

• Crystal growth of AlGaN semiconductors and development of deep-UV light-emitting diodes (DUV-LEDs)
• Development of deep-UV laser diodes (DUV-LDs)
• Development of terahertz quantum-cascade lasers (THz-QCLs) using GaAs and GaN-based semiconductors

Publications

1. Lin, T.T., Ying, L., and Hirayama, H.:
   "Threshold current density reduction by utilizing high-Al-composition barriers in 3.7 THz GaAs/AlGaAs quantum cascade lasers"
   Appl. Phys. Express, Vol. 5, 012101 (2011)
2. Mino, T., Hirayama, H., Takano, T., Tsubaki, K., and Sugiyama, M.:
   "Realization of 256-278 nm AlGaN-based Deep-Ultraviolet Light-Emitting Diodes on Si Substrates Using Epitaxial Lateral Overgrowth AlN Templates"
   Appl. Phys. Express 4, 092104 (2011)
3. Fujikawa, S., and Hirayama, H.:
   "284-300 nm Quaternary InAlGaN-based Deep-Ultraviolet Light-Emitting Diodes on Si (111) Substrates"
   Appl. Phys. Express, 4 061002 (2011)
4. Terashima, W. and Hirayama, H.:
   "The Utility of Droplet Elimination by Thermal Annealing Technique for Fabrication of GaN/AlGaN Terahertz Quantum Cascade Structure by Radio Frequency Molecular Beam Epitaxy"
   Appl. Phys. Express, Vol. 3, No. 12, 125501-1-3 (2010)
5. Hirayama, H., Noguchi, N., and Kamata, N.:
   "222 nm Deep-Ultraviolet AlGaN Quantum Well Light-Emitting Diode with Vertical Emission Properties"
   Appl. Phys. Express, 3, 032102 (2010)
6. Hirayama, H., Tsukada, Y., Maeda, N., and Kamata, N.:
   "Marked Enhancement in the Efficiency of Deep-Ultraviolet AlGaN Light-Emitting Diodes by Using a Multiquantum-Barrier Electron Blocking Layer"
   Appl. Phys. Express, 3, 031002 (2010)
7. Hirayama, H., Noguchi, N., Fujikawa, S., Norimatsu, J., Takano, T., Tsubaki, K., and Kamata, N.:
   "222-282nm AlGaN and InAlGaN based high-efficiency deep-UV-LEDs fabricated on high-quality AlN on sapphire"
   Physica Status Solidi (a), 206, pp. 1176-1182 (2009)
8. Hirayama, H., Noguchi, N., Yatabe, T., and Kamata, N.:
   "227 nm AlGaN light-emitting diode with 0.15 mW output power realized using thin quantum well and AlN buffer with reduced threading dislocation density"
   Appl. Phys. Express, 1, 051101 (2008)
9. Hirayama, H., Yatabe, T., Noguchi, N., Ohashi, T., and Kamata, N.:
   "231-261nm AlGaN deep-ultraviolet light-emitting diodes fabricated on AlN multilayer buffers grown by ammonia pulse-flow method on sapphire"
   Appl. Phys. Lett. 91, 071901 (2007)
10. Hirayama, H.:
    "Quaternary InAlGaN-based high-efficiency ultraviolet light-emitting diodes"
    J. Appl. Phys. Vol. 97, pp. 091101 1-19 (2005). (Focused Review: Invited Paper)