RT CW operation of InGaN multi-quantum-well structure laser diodes

Gallium nitride and other III–Vnitride-based semiconductors have a direct band gap that is suitable for blue light-emitting devices. The band gap energy of aluminium gallium indium nitride (AIInGaN) varies between 6.2 and 2.0 eV, depending on its composition at room temperature. Thus, using these semiconductors, red to UV emitting devices are fabricated. High efficient UV, blue and green InGaN single-quantum-well (SQW) structure light-emitting diodes (LEDs) have been fabricated with the external quantum efficiencies of 7.5% at 371 nm (UV), 11.2% at 468 nm (blue) and 11.6% at 520 nm (green), respectively, which were the highest values ever reported for the LEDs with those shorter emission wavelengths. The luminous efficiencies of blue and green LEDs were 5 lm/W and 30 lm/W, respectively, which values are almost identical to that of the white conventional incandescent bulb lamp (20 lm/W). By combining the blue, green and red LEDs, we could fabricate white LEDs with a luminous efficiency of 20–30 im/W which is almost comparable to that of the incandescent bulb lamp. Thus, we can replace the conventional incandescent bulb lamps with these LEDs in order to save an energy consumption and natural resources now.