GaN Superior for Short-Wavelength LEDs

A team of researchers from General Electric Global Research Center in Niskayuna, N.Y., and from AXT Optoelectronics in Monterey Park, Calif., has reported that blue and near-ultraviolet InGaN/GaN LEDs grown on GaN perform significantly better than those grown on sapphire. A report of the work, which may have an impact on solid-state lighting, appeared in the May 24 issue of Applied Physics Letters.

The researchers compared LEDs grown on sapphire and on a free-standing GaN substrate. The blue emitters displayed similar internal quantum efficiencies at an operating current of 20 mA, and the UV LED grown on GaN had an internal quantum efficiency twice that of the one on sapphire. At injection currents of up to 300 mA, the LEDs on GaN exhibited much higher output powers than their counterparts, which the scientists attributed to improved radiative efficiency, heat dissipation and current spreading.