SAGA UNIVERSITY
POWER ELECTRONICS LABORATORY (Prof. Kasu)

SiC, Nitride Power Device

 This figure shows on-site resistance (R_ON) and breakdown voltage (V_B) of power transistors with various semiconductors. The on-site resistance determines energy consumption during on state, and the breakdown voltage determines the high limit of operation voltage, thus the output power. The relation of the Ron and the V_B is trade-off. The conventional silicon devices operate in green area.
 In order to achieve both high energy efficiency and high output power, we choose SiC (green), GaN (blue), AlN (violet), and diamond (red).

 Therefore, we are focusing on high-quality SiC, GaN, AlN, diamond and achieve p-type and n-type semiconductors and fabricate power transistors.

 We will measure fundamental electric properties such as carrier mobility and breakdown voltage, investigate fundamental physics of such wide-gap semiconductors.

 Next with molecular beam epitaxy (MBE), we fabricate atomic-scale controlled GaN, AlN semiconductors.

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Diamond Power Transistors

 Diamond is called the ultimate power semiconductor because it intrinsically has many superior physical properties over conventional semiconductors.

 First, we will be making diamond single-crystal in a wafer size. Then we grow p-type and n-type diamond semiconductors.
We will clarify electronic properties of diamond semiconductor and fabricate diamond power transistors.

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Wide-Gap Semiconductor Power-Control Circuit

 Power-control circuit such as inverters operates in hundreds KHz and MHz range, and therefore its switching characteristics are important and is closely related with semiconductor’s electronic properties.

 First, we will fabricate power-control circuit of wide-gap semiconductors such as SiC and GaN, and diamond.

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Diamond NV Center as Quantum Memory

 Recently quantum computer and communication draw much attention. Quantum computer can operate quantum information processing with 'quantum bit'. It will solve complicated factoring algorithm much faster than conventional computers.

 NV center is nitrogen-vacancy complex in diamond crystal. Negatively-charged NV center can be observed as light emission with a wavelength of 637 nm zero-phonon line (ZPL) and electron captured by NV center has energy split at 2.88 GHz and its energy is similar to energy required for quantum bit.

 We will make nitrogen-doped diamond crystal best suitable for quantum memory.

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