Masahito Kanamura

High temperature (>400 K) ferromagnetism in III–V-based diluted magnetic semiconductor GaCrN grown by ECR molecular-beam epitaxy

A new III–V nitride-based diluted magnetic semiconductor GaCrN has been successfully synthesized for the first time. X-ray diffraction measurement showed no existence of secondary phase in the GaCrN layers. They showed a ferromagnetic behavior with the Curie temperature of higher than 400 K, and clear saturation and hysteresis were observed in the magnetization versus magnetic field curves at all measuring temperatures (10–400 K). Specially, GaCrN magnetization data show no paramagnetic component at low temperature, which are superior characteristics over GaMnN. Photoluminescence emission from GaCrN layer was observed at around 3.29 eV at 10–300 K.

600 V JEDEC-qualified highly reliable GaN HEMTs on Si substrates

In this paper, we demonstrate 600 V highly reliable GaN high electron mobility transistors (HEMTs) on Si substrates. GaN on Si technologies are most important for the mass-production at the Si-LSI manufacturing facility. High breakdown voltage over 1500 V was confirmed with stable dynamic on-resistance (RON) using cascode configuration package. These GaN HEMT on Si based cascode packages have passed the qualification based on the standards of the Joint Electron Devices Engineering Council (JEDEC) (1-5) for the first time. High voltage acceleration test was performed up to 1150 V. Even considering most conservative failure mechanism, mean time to failure (MTTF) of over 1×107 hours at 600 V was predicted at 80°C. Additional conclusion is that conventional packages such as TO-220 are still suitable for high speed circuit application without using a specific gate driver. Ultimately GaN will significantly reduce conversion losses endemic in all areas of electricity conversion, ranging from power supplies to PV inverters to motion control to electric vehicles, enabling consumers, utilities and governments to contribute towards a more energy efficient world.

Effect of Atomic-Layer-Deposition Method on Threshold Voltage Shift in AlGaN/GaN Metal–Insulator–Semiconductor High Electron Mobility Transistors

We have investigated the mechanism for threshold voltage (Vth) shift of AlGaN/GaN metal–insulator–semiconductor high electron mobility transistors (MIS-HEMTs) for power applications. In this study, atomic layer deposited (ALD)-Al2O3 was used in AlGaN/GaN MIS-HEMTs as gate insulator films, and we focused on plasma-induced damages at the GaN/Al2O3 interface, when O2 plasma was used as the oxidant source for the ALD method. We clarified that the deep trap sites which were located around 2.58–3.26 eV from the conduction band edge were generated in the oxidized-GaN layer at the GaN/Al2O3 interface due to plasma-induced damages, and this caused the Vth shift when using O2 plasma. Therefore, we controlled the initial oxidant source, and demonstrated the reductions in the Vth shift and the gate leakage current by applying hybrid–Al2O3 structure (lower H2O vapor–Al2O3/upper O2 plasma–Al2O3) for AlGaN/GaN MIS-HEMTs.

Growth of InMnAsSb:InSb Heterostructures with Mid-Infrared-Light-Induced Ferromagnetic Properties

New diluted magnetic semiconductor InMnAsSb/InSb heterostructures were proposed and grown on InAs substrates by low-temperature molecular beam epitaxy. Raman scattering measurements indicated that an InMnAsSb layer grown on InSb at 250°C has higher crystal quality than that grown at 280°C. By the irradiation of light with a wavelength longer than 2 µm at low temperatures, the magnetization was increased and this light-induced magnetization remained even after the light irradiation ceased. Corresponding to the Raman data, better light-induced ferromagnetic ordering was observed for the samples grown at 250°C.

Growth of InMnAsSb/InSb heterostructures with mid-infrared light-induced ferromagnetic properties

New diluted magnetic semiconductor InMnAsSb/InSb heterostructures were proposed and grown an InAs substrates by low-temperature molecular beam epitaxy. Raman scattering measurements show that InMnAsSb layer grown on InSb at 250/spl deg/C has higher crystal quality than that grown at 280/spl deg/C. Light-induced ferromagnetic order was observed, for the first time, when these samples were illuminated with the light of wavelengths longer than 2 /spl mu/m. Corresponding to the Raman data, better light-induced ferromagnetic order was for the 250/spl deg/C-grown samples. The long-term preservation of the ferromagnetic order was confirmed even after the light-off.