Stimulated emission hits 474 nm from semipolar InGaN diodes

Pure green light-emitting diodes (LEDs) have great potential in displays and as pump sources, and high-powered ones could become an alternative to expensive argon-ion lasers and solid-state lasers. Toward this goal, researchers at Kyoto University (Kyoto, Japan) and Nichia (Tokushima, Japan) have demonstrated stimulated emission ranging from 405 to 474 nm at room temperature from three semipolar indium gallium nitride (InGaN) diode structures. Crystal growth of indium-rich InGaN quantum wells on a nonpolar plane is difficult due to its lack of polarity, but a semipolar (1122) GaN substrate is an ideal choice for easy crystal growth. Elimination of the quantum-confinement Stark effect (QCSE) is another bonus of semipolar planes, says team member Kazunobu Kojima, which translates to a low-threshold current of 175 to 200 kW/cm² and correlated high output power of 5.0 to 525 kW/cm². The active layer of InGaN quantum wells measures only 2 nm. The next step for the Kyoto/Nichia effort is to fabricate pure green laser-diode chips, and to extend the wavelength to 520 nm. Contact Kazunobu Kojima at [email protected].