Less strained and more efficient GaN light-emitting diodes with embedded silica hollow nanospheres

Light-emitting diodes (LEDs) become an attractive alternative to conventional light sources due to high efficiency and long lifetime. However, different material properties between GaN and sapphire cause several problems such as high defect density in GaN, serious wafer bowing, particularly in large-area wafers, and poor light extraction of GaN-based LEDs. Here, we suggest a new growth strategy for high efficiency LEDs by incorporating silica hollow nanospheres (S-HNS). In this strategy, S-HNSs were introduced as a monolayer on a sapphire substrate and the subsequent growth of GaN by metalorganic chemical vapor deposition results in improved crystal quality due to nano-scale lateral epitaxial overgrowth. Moreover, well-defined voids embedded at the GaN/sapphire interface help scatter lights effectively for improved light extraction, and reduce wafer bowing due to partial alleviation of compressive stress in GaN. The incorporation of S-HNS into LEDs is thus quite advantageous in achieving high efficiency LEDs for solid-state lighting.This work was supported by the Brain Korea 21 (BK21) Program, two World Class University (WCU) Programs (R31-2008-000-10075-0 & R31-10013) of the Ministry of Education of Korea, and the Technology Innovation Program (Industrial Strategic Technology Development Program (10031885) funded by the Ministry of Knowledge Economy, Korea. K. C. and H. W. also acknowledges the financial support from the National Creative Research Initiative Program for "Intelligent Hybrids Research Center'' (No. 2010-0018290) through the National Research Foundation of Korea (NRF) funded by the Korean Ministry of Education, Science, and Technology (MEST). LED processing and characterizations were performed at the Research Institute for Advanced Materials, SNU, and the Korea Advanced Nanofabrication Center, located in Suwon, Korea. H. H. was supported by Basic Science Research Program through the National Research Foundation in Korea funded by the Ministry of Science, ICT and Future Planning (2013008806)