[1] G Deng, Y Zhang, Y Yu et al. Significantly reduced in-plane tensile stress of GaN films grown on SiC substrates by using graded AlGaN buffer and SiN_x interlayer. Superlattices Microstruct, 122, 74(2018).

[2] L Yan, Y Zhang, X Han et al. Polarization-induced hole doping in N-polar III-nitride LED grown by metalorganic chemical vapor deposition. Appl Phys Lett, 112, 182104(2018).

[3] G Deng, Y Zhang, Y Yu et al. Significantly improved surface morphology of N-polar GaN film grown on SiC substrate by the optimization of V/III ratio. Appl Phys Lett, 112, 151607(2018).

[4] G Deng, Y Zhang, Y Yu et al. Study on the structural, optical, and electrical properties of the yellow light-emitting diode grown on free-standing (0001) GaN substrate. Superlattices Microstruct, 116, 1(2018).

[5] L Junlin, Z Jianli, W Guangxu et al. Status of GaN-based green light-emitting diodes. Chin Phys B, 24, 39(2015).

[6] M H Crawford. LEDs for solid-state lighting: performance challenges and recent advances. IEEE J Sel Top Quantum Electron, 15, 1028(2009).

[7] J Piprek. Origin of InGaN/GaN light-emitting diode efficiency improvements using tunnel-junction-cascaded active regions. Appl Phys Lett, 104, 2217(2014).

[8] A Hangleiter, F Hitzel, C Netzel et al. Suppression of nonradiative recombination by V-shaped pits in GaInN/GaN quantum wells produces a large increase in the light emission efficiency. Phys Rev Lett, 95, 127402(2005).

[9] Z Quan, L Wang, C Zheng et al. Roles of V-shaped pits on the improvement of quantum efficiency in InGaN/GaN multiple quantum well light-emitting diodes. J Appl Phys, 116, A779(2014).

[10] Y Li, F Yun, X Su et al. Deep hole injection assisted by large V-shape pits in InGaN/GaN multiple-quantum-wells blue light-emitting diodes. J Appl Phys, 116, 253512(2014).

[11] S Zhou, X Liu. Effect of V-pits embedded InGaN/GaN superlattices on optical and electrical properties of GaN-based green light-emitting diodes. Phys Status Solidi Appl Res, 214, 1770125(2016).

[12] H Takahashi, A Ito, T Tanaka et al. Effect of intentionally formed `V-defects' on the emission efficiency of GaInN single. Jpn Soc Appl Phys, 39, 569(2000).

[13] S M Ting, J C Ramer, D I Florescu et al. Morphological evolution of InGaN/GaN quantum-well heterostructures grown by metalorganic chemical vapor deposition. J Appl Phys, 94, 1461(2003).

[14] L C Le, D G Zhao, D S Jiang et al. Effect of V-defects on the performance deterioration of InGaN/GaN multiple-quantum-well light-emitting diodes with varying barrier layer thickness. J Appl Phys, 114, 143706(2013).

[15] Q Lv, J Liu, C Mo et al. Realization of highly efficient InGaN green LEDs with sandwich-like multiple quantum well structure: role of enhanced interwell carrier transport. ACS Photonics, 6, 130(2018).

[16] G Wang, X Tao, J Liu et al. Temperature-dependent electroluminescence from InGaN/GaN green light-emitting diodes on silicon with different quantum-well structures. Semicond Sci Technol, 30, 15018(2014).

[17] X Wu, J Liu, Z Quan et al. Electroluminescence from the sidewall quantum wells in the V-shaped pits of InGaN light emitting diodes. Appl Phys Lett, 104, 1634(2014).

[18] J Kim, Y Tak, J Kim et al. Analysis of forward tunneling current in InGaN/GaN multiple quantum well light-emitting diodes grown on Si (111) substrate. J Appl Phys, 114, 231107(2013).

[19] P Kozodoy, H Xing, S P Denbaars et al. Heavy doping effects in Mg-doped GaN. J Appl Phys, 87, 1832(2000).

[20] W Xiaoming. Study on the luminescence properties of V-pits-containing GaN based blue LEDs on Si substrates. Nanchang University(2014).

[21] E F Schubert, T Gessmann. Light emitting diodes. Encylopedia of Condensed Matter Physics, 102(2005).