Nonpolar/Semipolar GaN Technology for Violet, Blue, and Green Laser Diodes

摘要

To achieve 520-532 nm green laser diodes (LDs), nonpolar and semipolar nitrides have attracted much attention because their usage leads to the elimination of the quantum-confined Stark effect and higher optical gains in this wavelength region. Since the breakthrough in the homoepitaxial growth technology for them, many nonpolar m-plane devices such as mW-class blue light-emitting diodes, violet 405 nm LDs, blue 460 nm LDs, and blue-green LDs beyond 490 nm have been announced. Advantages such as small blueshift and high slope efficiency (high output power to injected current ratio) have been confirmed for the first time in m-plane LDs beyond the blue region. On the other hand, the semipolar plane is also a candidate for green LDs. The pulsed operation of semipolar (tOTT) and (1122) violet LDs and lasing for a (1122) LD at 514 nm by optical pumping also have been reported. Such rapid progress in this research field will be reviewed.