Current Status of GaN-Based Solid-State Lighting

The continuous improvement in luminous efficacy of white light-emitting-diode (LED) sources offers the potential of considerable energy savings in general lighting applications. Recent experiments at UCSB have demonstrated 117 lumens per watt (m/W) in white LEDs, with further improvements expected in the near future. Considerable progress has also been achieved using nonpolar GaN, such as a-plane {1120} and m-plane {1100} GaN, or semipolar GaN substrates. Such devices avoid the deleterious effects of charge separation due to spontaneous and piezoelectric polarization inherent in most c-axis oriented devices.