Non polar GaN LED performance was an important breakthrough

In May 1st 007, California University of Santa Barbara (UCSB) GaN non-polar materials research group (by Nakamura Shuji [Shuji and Steven DenBaars Nakamura] Leadership) made of blue purple light InGaN LED record high in high power output current, the external quantum efficiency and also has 41% (EQE). The multi quantum well structure LED prepared by the UCSB research group, the output power of 28mW at 20mA, the peak wavelength is 402nm, EQE is equivalent to 45.4%. Fatefully, the device can still keep high conversion efficiency at high current (200mA, output power is 250mW), the current density from 1 A/cm2 up to 350 A/cm2, external quantum efficiency is only slightly decreased. The development of crystal structure on the M plane to develop nonpolar GaN has long been regarded as one of the ways to improve the performance of LED and lasers. But until now, the nonpolar GaN chip based on both in efficiency and output power are behind the traditional structure. And the performance of the non-polar GaN can make great progress thanks to the development of M surface GaN substrate (provided by MITSUBISHI, Japan). The substrate material is obtained by slicing the C surface GaN grown by the HVPE method. Despite a major breakthrough, the UCSB team says there is room for improvement in the performance of nonpolar GaN. In the latest research results, LED chips were prepared by standard treatment process, and the use of ITO transparent electrode, which indicates that the external quantum efficiency and potential for improvement. However, in order to realize the commercialization of the nonpolar devices, there are still many technical challenges, and the high quality m surface GaN substrate is one of the obstacles. M GaN substrate UCSB group used only 1 square centimeters, in contrast to the common use of the 2 inch diameter substrate materials, such as production equipment for MOCVD preparation, m surface of the GaN substrate size is too small too too expensive.