Materials Design Division

Physics of Electronic Materials

Takashi MATSUOKA

Prof.Takashi MATSUOKA

  • Senior Assist. Prof. Tomoyuki TANIKAWA
  • Assist. Prof. Takashi HANADA
  • Assist. Prof. Shigeyuki KUBOYA

Creation of Innovative Energy-Saving Devices by Development of Crystal Growth Technology and Control of Physical Properties of Nitride Semiconductors

Our target is to develop new electronic materials which can open up novel device applications. The material of our current interest is a nitride semiconductor, lnGaAIN system, which is well known as a material for blue light-emittingdiodes (LEDs). Taking advantages of our epitaxial growth reactors developed by ourselves and a series of device fabrication equipment, we are going toward the further contribution to the global societies in terms of the energy saving, by developing high-power electronic devices and high-efficiency light-emitting devices.

It has been a major problem of the significant energy loss in the recent accelerated applications to the electric vehicles and smart grid systems. The cause is clear that the low efficiency in the current switching devices on the inverters and power conditioners. We are aiming to develop nitrogenpolar inverted-channel high electron mobility transistors, which are expected to have much lower energy loss that that of conventional group-III-polar devices, in order to contribute to the global societies in terms of the promotion for further energy saving.

nitride semiconductors, epitaxial growth, electronic devices, light-emitting devices, polarity, three-dimensional intensity mapping of dislocations
Figure 1: Polarity of GaN. The N-polar (0001) orientation has the reversed polarization, which allows us to explore a novel device design.

Polarity of GaN. The N-polar (0001) orientation has the reversed polarization, which allows us to explore a novel device design.

Figure 2: Schematic structures of high electron mobility transistor (HEMT)

Schematic structures of high electron mobility transistor (HEMT)

Figure 3: Three-dimensional image of threading dislocations in GaN observed with multiphoton-excitation photoluminescence.

Three-dimensional image of threading dislocations in GaN observed with multiphoton-excitation photoluminescence. At the focal point of an incident laser as an excitation source, carriers are generated and emit photons through the recombination process. The emission intensity decreases around dislocations. By scanning the laser beam, the three-dimensional intensity mapping can be obtained, in other words, the distribution of the dislocations can be observed. The feature of this method enables to three-dimensionally investigate the distribution of dislocations in GaN without any destructive preparation for a sample.

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