The University of Tokyo · Physics and Astronomy
Professor Hiroshi Fujioka's research lab specializes in the development of high-quality III-nitride semiconductors, particularly gallium nitride (GaN), using pulsed sputtering deposition for large-area and flexible electronic and optoelectronic devices. The lab focuses on innovative epitaxial growth techniques on unconventional substrates such as multilayer graphene, amorphous SiO2, and flexible metal foils to enable low-cost, scalable fabrication. Key research directions include polarity control of GaN, heteroepitaxial growth with AlN interlayers, and the integration of degenerate GaN contacts for high-performance high-electron-mobility transistors (HEMTs) and light-emitting diodes (LEDs). The ultimate goal is to advance next-generation GaN-based devices for energy-efficient lighting, high-frequency electronics, and flexible displays.
Figures are computed from collected data and may differ slightly.
GaN films were grown on a multilayer graphene (MLG)/amorphous SiO2 stack by pulsed sputtering deposition and their structural properties were investigated. The GaN films on MLG show high c-axis orientation. In addition, the GaN films exhibit coexisting zincblende and wurtzite phases, but the zincblende phase is suppressed by the insertion of AlN interlayers. The polarity control of the GaN films was demonstrated using AlN interlayers with and without surface oxidation. These results indicate tha
Abstract This paper reports AlN barrier Al 0.5 Ga 0.5 N high electron mobility transistors (HEMTs) with heavily Si-doped degenerate GaN contacts prepared by pulsed sputtering deposition. Selectively regrown n-type GaN contacts exhibit typical degenerate properties with the electron concentration and mobility of 2.6 × 10 20 cm −3 and 115 cm 2 V −1 s −1 , respectively, resulting in a record low contact resistance R C of 0.43 Ω mm for the AlN/Al 0.5 Ga 0.5 N HEMTs. The AlN/Al 0.5 Ga 0.5 N HEMTs dis
GaN-based light-emitting diodes (LEDs) have been widely accepted as highly efficient solid-state light sources capable of replacing conventional incandescent and fluorescent lamps. However, their applications are limited to small devices because their fabrication process is expensive as it involves epitaxial growth of GaN by metal-organic chemical vapor deposition (MOCVD) on single crystalline sapphire wafers. If a low-cost epitaxial growth process such as sputtering on a metal foil can be used,
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