A method for laser-induced local p-type activation of an as-grown Mg-doped GaN sample with a high lateral resolution is developed for realizing high power vertical devices for the first time. As-grown Mg-doped GaN is converted to p-type GaN in a confined local area. The transition from an insulating to a p-type area is realized to take place within about 1–2 μm fine resolution. The results show that the technique can be applied in fabricating the devices such as vertical field effect transistors, vertical bipolar transistors and vertical Schottkey diode so on with a current confinement region using a p-type carrier-blocking layer formed by this technique.
A dynamically controlled micro-plasma-excited (MIPE) aluminum gallium nitride deep ultraviolet (DUV) light-emitting device is demonstrated. This device provides high-power DUV emission at any desired wavelength and allows enlargement of emission areas like plasma display panels for easy, low-cost fabrication. Neither p-n junctions nor electrode contacts are required for device fabrication. We fabricated 2-in. diameter wafer-size MIPE emitters of DUV light at specific wavelengths from AlGaN quantum wells with 50 mW average output power. We can also fabricate 6-in. diameter DUV emitters using sapphire wafers and 1 m × 5 m panel-type DUV emitters.
A conductive AlN epitaxial layer is successfully realized by spontaneously forming via-holes filled with n-AlGaN inside an AlN buffer layer on a Si substrate. The via-holes are found to originate from the formation of an Al–Si alloy, produced from a small amount of Al supplied to the Si substrate at the initial stage of the crystal growth of the n-AlN buffer layer using metal organic chemical vapor deposition and successive selective growth of n-AlN on the Si surface. The via-holes are filled with conductive n-AlGaN by successive epitaxial growth of n-AlGaN, making the insulating n-AlN buffer layer conductive. The vertical conductivity through this n-AlN buffer layer is enhanced more than 540 times compared with an n-AlN buffer layer without via-holes. Using this conductive n-AlN buffer layer on the Si substrate, we successfully fabricated a vertical n-AlGaN Schottky diode on the Si substrate for the first time.
We have succeeded in developing a new dynamic microplasma-excited deep ultraviolet light emitting device using aluminum gallium nitride (AlGaN) multi-quantum wells (MIPE). The operating principle is completely different from that of current injection-type deep ultraviolet light emitting diodes. We have created a 12 × 5.5 cm device with a power of about 1 W at a wavelength of 325 nm. We can achieve panel-type laminar-flow water purification and cleaning systems that can be alternatives to the use of mercury lamps as a DUV light source, since these cannot be used under the Minamata Treaty. The wavelength region from 210 nm to 250 nm realized in this device opens new fields of academic research and areas of application, in which the decomposition of materials that are difficult to break down, the synthesis of new materials, including a new H 2 battery cell, and disinfection of water are possible. C⃝ 2016 Wiley Periodicals, Inc. Electron Comm Jpn, 99(7): 3-11, 2016; Published online in Wiley Online Library (wileyonlinelibrary.com).
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