Jiro Shinkai

Effects of strained-layer structures on the threshold current density of AlGaInP/GaInP visible lasers

We have investigated the effects of strained‐layer structures on the reduction of the threshold current density of AlGaInP/GaInP visible laser diodes. It was found that a remarkable reduction of the threshold current density could be realized by incorporating strained single quantum well structures in their active regions. The minimum threshold current density at room temperature under pulsed conditions is 215 A/cm2, which is by far the lowest value ever reported for AlGaInP/GaInP visible lasers and comparable to those of AlGaAs/GaAs lasers.

High temperature (≳150 °C) and low threshold current operation of AlGaInP/GaxIn1−xP strained multiple quantum well visible laser diodes

High temperature and very low threshold current operation of a separate confinement heterostructure (SCH) AlGaInP/GaxIn1−xP (x=0.43) strained multiple quantum well (SMQW) lasers has been achieved. Continuous wave (cw) operation was observed up to at least 150 °C with an output power of more than 7 mW, which is the highest cw operating temperature ever reported for devices operating in the visible wavelength region. The characteristic temperature between 20 and 80 °C was 130 K. The threshold current and threshold current density at 25 °C were 13.9 mA for a 5×160 μm device and 430 A/cm2 for a 80×770 μm device.

High Temperature Characteristics of 4H-SiC RESURF-Type JFET

400V/2.5A 4H-SiC JFETs having a reduced surface field (RESURF) structure were fabricated. Measurements on the on-resistance, blocking and switching characteristics at high temperature were carried out. It was confirmed that the JFET has smaller dependence of on-resistance on temperature than a Si-MOSFET and positive temperature dependence of the breakdown voltage. It was also confirmed that the JFET has fast switching characteristics, that is, the turn-on and turn-off times are about 15 ns and 10 ns, at 200 °C as well as at 25 °C. A demonstration of a DC-DC converter using a module consisting of the JFET was carried out at a junction temperature of 200 °C. Stable continuous switching operation of the JFET at a junction temperature of 200 °C was confirmed.

Fabrication of a multi-chip module of 4H-SiC RESURF-type JFETs

We fabricated a multi-chip module of 4H-SiC reduced surface field (RESURF)-type lateral JFETs. A single chip consists of 4 unit devices of 2.0 mm × 0.5 mm in size, which were isolated electrically from each other. The multi-chip module consists of 8 chips mounted on an AMC substrate. The drain current and the breakdown voltage of the module are over 3 A and 771 V, respectively. The turn-on time and the turn-off time are 36ns and 166ns, respectively. The module resistance is proportional to the absolute temperature to the 1.05th power.