Full-Color III-Nitride Nanowire Light-Emitting Diodes

Abstract

III-nitride nanowire based lightemitting diodes (LEDs) have been intensively studied as promising candidates for future lighting technologies. Compared to conventional GaN-based planar LEDs, III-nitride nanowire LEDs exhibit numerous advantages including greatly reduced dislocation densities, polarization elds, and quantum-con ned Stark e ect due to the e ective lateral stress relaxation, promising high e ciency full-color LEDs. Beside these advantages, however, several issues have been identi ed as the limiting factors for further enhancing the nanowire LED quantum e ciency and light output power. Some of the most probable causes have been identi ed as due to the lack of carrier con nement in the active region, non-uniform carrier distribution, electron over ow, and the nonradiative recombination along the nanowire lateral surfaces. Moreover, the presence of large surface states and defects contribute signi cantly to the carrier loss in nanowire LEDs. Consequently, reported nanowire LEDs show relatively low output power. Recently, III-nitride core-shell nanowire LED structures have been reported as the most e cient nanowire white LEDs with a record high output power which is more than 500 times stronger than that of nanowire white LEDs without using core-shell structure. In this context, we will review the current status, challenges and approaches for the high performance IIInitride nanowire LEDs. More speci cally, we will describe the current methods for the fabrication of nanowire structures including top-down and bottom-up approaches, followed by characteristics of III-nitride nanowire LEDs. We will then discuss the carrier dynamics and loss mechanism in nanowire LEDs. The typical designs for the enhanced performance of III-nitride nanowire LEDs will be presented next. The color tunable nanowire LEDs with emission wavelengths in the visible spectrum, and phosphorfree nanowire white LEDs will be nally discussed.