InGaN/GaN Multi-Quantum-Well and Light-Emitting Diode Based on   V-pit-Shaped GaN Grown on Patterned Sapphire Substrate
  V-pit-defects in GaN-based light-emitting diodes induced by dislocations are considered beneficial to electroluminescence because they relax the strain in InGaN quantum wells and also enhance the hole lateral injection through sidewall of V-pits. In this paper, regularly arranged V-pits are formed on c-plane GaN grown by metal organic vapor phase epitaxy on conventional c-plane cone-patterned sapphire substrates. The size of V-pits and area of flat GaN can be adjusted by changing growth temperature. Five pairs of InGaN/GaN multi-quantumwell and also a light-emitting diode structure are grown on this V-pit-shaped GaN. Two peaks around 410 nm and 450 nm appearing in both photoluminescence and cathodeluminescence spectra are from the semipolar InGaN/GaN multi-quantum-well on sidewalls of V-pits and cplane InGaN/GaN multi-quantum-well, respectively. In addition, dense bright spots can be observed on the surface of light-emitting diode when it works under small injection current, which are believed owing to the enhanced hole injection around V-pits. 
Lai Wang, Xiao Meng, Di Yang, Zilan Wang, Zhibiao Hao, Yi Luo,   Changzheng Sun, Yanjun Han, Bing Xiong, Jian Wang and Hongt...
cond-mat.mes-hall physics.optics