Effect of V-Pits Coverage Optoelectronic Characteristics in Green GaN-Based Mini-Light-Emitting Diodes Grown by MOCVD

Abstract

V-pits have been intensively studied for their role in light-emitting diodes (LEDs). The coverage of V-pits in InGaN/GaN multi-quantum wells (MQWs) is critical for suppressing leakage path through electron blocking layer (EBL). In this study, we have investigated the coverage of V-pits in green mini-LEDs modulated via growth parameters optimization and systematically analyzed the characteristics of the photoelectric properties associated with V-pits coverage on device. Elevated temperatures and pressures result in enhanced adatoms migration, which can achieve a coverage up to 98.8% of V-pits, improving the crystal quality due to stable surface. Electrical characterization reveals that although high-coverage devices exhibit suppressed leakage current, their peak external quantum efficiency (EQE) decreases, more seriously spectral blue shift and operating voltage increase due to compromised hole transport uniformity. Intriguingly, intermediate-coverage samples demonstrate superior breakdown voltage characteristics. Current–voltage curve analysis shows the ideality factor increases from 1.8 to 2.5 with improved coverage, indicating aggravated Shockley–Read–Hall (SRH) recombination with covered V-pits.

Keywords

GaN / green LED / InGaN / miniaturization / multiple-quantum-wells / V-pits

References

[1] R. X. G. Ferreira, E. Xie, J. J. D. McKendry, et al., “High Bandwidth GaN-Based Micro-LEDs for Multi-Gb/s Visible Light Communications,” IEEE Photonics Technology Letter 28, no. 19 (2016): 2023–2026, https://doi.org/10.1109/LPT.2016.2581318.

[2] F. Feng, Y. Liu, K. Zhang, et al., “AlGaN Multiple Quantum Well Deep-Ultraviolet Micro-Light-Emitting Diodes for High Color Conversion Efficiency Quantum Dots Display,” Journal of the Society for Information Display 30, no. 7 (2022): 556–566, https://doi.org/10.1002/jsid.1107.

[3] Y. Liu, B.-R. Hyun, Y. Wang, K. Zhang, H. S. Kwok, and Z. Liu, “R/G/B Micro-LEDs for In-Pixel Integrated Arrays and Temperature Sensing,” ACS Applied Electronic Materials 3, no. 1 (2021): 3–10, https://doi.org/10.1021/acsaelm.0c00757.

[4] K. Wang, D. Huang, X. Li, et al., “Unconventional Strategies to Break Through the Efficiency of Light-Driven Water Splitting: A Review,” Electron 1, no. 1 (2023): e4, https://doi.org/10.1002/elt2.4.

[5] V. Uwihoreye, Y. Hu, G. Cao, X. Zhang, F. E. Oropeza, and K. H. L. Zhang, “Recent Progress on Heteroepitaxial Growth of Single Crystal Diamond Films,” Electron 2, no. 4 (2024): e70, https://doi.org/10.1002/elt2.70.

[6] K. Hölz, J. Lietard, and M. M. Somoza, “High-Power 365 nm UV LED Mercury Arc Lamp Replacement for Photochemistry and Chemical Photolithography,” ACS Sustainable Chemistry & Engineering 5, no. 1 (2017): 828–834, https://doi.org/10.1021/acssuschemeng.6b02175.

[7] F. Feng, Y. Liu, K. Zhang, et al., “High-Power AlGaN Deep-Ultraviolet Micro-Light-Emitting Diode Displays for Maskless Photolithography,” Nature Photonics 19, no. 1 (2025): 101–108, https://doi.org/10.1038/s41566-024-01551-7.

[8] H. Wu, X. Lin, Q. Shuai, et al., “Ultra-High Brightness Micro-LEDs With Wafer-Scale Uniform GaN-On-Silicon Epilayers,” Light: Science & Applications 13, no. 1 (2024): 284, https://doi.org/10.1038/s41377-024-01639-3.

[9] H. Jia, L. Guo, W. Wang, and H. Chen, “Recent Progress in GaN-Based Light-Emitting Diodes,” Advanced Materials 21, no. 45 (2009): 4641–4646, https://doi.org/10.1002/adma.200901349.

[10] X. Yang, L. Ma, L. Li, et al., “Towards Micro-PeLED Displays,” Nature Review Materials 8, no. 5 (2023): 341–353, https://doi.org/10.1038/s41578-022-00522-0.

[11] Y. Huang, E.-L. Hsiang, M.-Y. Deng, and S.-T. Wu, “Mini-LED, Micro-LED and OLED Displays: Present Status and Future Perspectives,” Light: Science & Applications 9, no. 1 (2020): 105, https://doi.org/10.1038/s41377-020-0341-9.

[12] V. K. Bandari and O. G. Schmidt, “A Bright Future for Micro-LED Displays,” Light: Science & Applications 13, no. 1 (2024): 317, https://doi.org/10.1038/s41377-024-01683-z.

[13] S. Gao, C. Lu, D. Guo, et al., “Optimizing Etching Depth for Ultra-High Brightness Green Micro-LED Display Development,” AIP Advances 14, no. 8 (2024): 085307, https://doi.org/10.1063/5.0213539.

[14] P. Li, J. Ewing, M. S. Wong, et al., “Advances in InGaN-Based RGB Micro-Light-Emitting Diodes for AR Applications: Status and Perspective,” APL Materials 12, no. 8 (2024): 080901, https://doi.org/10.1063/5.0222618.

[15] S. Mohan, J. Jeong, M. Kim, et al., “Size-Dependent Characteristics of InGaN-Based Blue and Green Micro-Light-Emitting Diodes,” Physica Status Solidi 221, no. 13 (2024): 2300642, https://doi.org/10.1002/pssa.202300642.

[16] S. S. Konoplev, K. A. Bulashevich, and S. Y. Karpov, “From Large-Size to Micro-LEDs: Scaling Trends Revealed by Modeling,” Physica Status Solidi 215, no. 10 (2018): 1700508, https://doi.org/10.1002/pssa.201700508.

[17] F. Olivier, S. Tirano, L. Dupré, et al., “Influence of Size-Reduction on the Performances of GaN-Based Micro-LEDs for Display Application,” Journal of Luminescence 191 (2017): 112–116, https://doi.org/10.1016/j.jlumin.2016.09.052.

[18] C. Zhang, Y. Wu, B. Xia, P. Su, and J. Ma, “Improvement in Quantum Efficiency of Green GaN-Based Micro-LED by Trapezoidal Quantum Well,” Journal of Luminescence 263 (2023): 120027, https://doi.org/10.1016/j.jlumin.2023.120027.

[19] H. Li, M. S. Wong, M. Khoury, et al., “Study of Efficient Semipolar (11-22) InGaN Green Micro-Light-Emitting Diodes on High-Quality (11-22) GaN/Sapphire Template,” Optics Express 27, no. 17 (2019): 24154, https://doi.org/10.1364/OE.27.024154.

[20] L. Yu, B. Lu, P. Yu, et al., “Ultra-Small Size (1-20 μm) Blue and Green Micro-LEDs Fabricated by Laser Direct Writing Lithography,” Applied Physics Letters 121, no. 4 (2022): 042106, https://doi.org/10.1063/5.0099642.

[21] C. Zhao, C. W. Tang, B. Lai, G. Cheng, J. Wang, and K. M. Lau, “Low-Efficiency-Droop InGaN Quantum Dot Light-Emitting Diodes Operating in the ‘Green Gap’,” Photonics Research 8, no. 5 (2020): 750, https://doi.org/10.1364/PRJ.380158.

[22] Q. Wang, X. Gao, Y. Xu, and J. Leng, “Carrier Localization in Strong Phase-Separated InGaN/GaN Multiple-Quantum-Well Dual-Wavelength LEDs,” Journal of Alloys and Compounds 726 (2017): 460–465, https://doi.org/10.1016/j.jallcom.2017.07.326.

[23] S. Zhu, S. Lin, J. Li, et al., “Influence of Quantum Confined Stark Effect and Carrier Localization Effect on Modulation Bandwidth for GaN-based LEDs,” Applied Physics Letters 111, no. 17 (2017): 171105, https://doi.org/10.1063/1.4993230.

[24] S.-C. Tsai, C.-H. Lu, and C.-P. Liu, “Piezoelectric Effect on Compensation of the Quantum-Confined Stark Effect in InGaN/GaN Multiple Quantum Wells Based Green Light-Emitting Diodes,” Nano Energy 28 (2016): 373–379, https://doi.org/10.1016/j.nanoen.2016.08.061.

[25] M. S. Wong, C. Lee, D. J. Myers, et al., “Size-Independent Peak Efficiency of III-Nitride Micro-Light-Emitting-Diodes Using Chemical Treatment and Sidewall Passivation,” Applied Physics Express 12, no. 9 (2019): 097004, https://doi.org/10.7567/1882-0786/ab3949.

[26] S. Nakamura, “The Roles of Structural Imperfections in InGaN-Based Blue Light-Emitting Diodes and Laser Diodes,” Science 281, no. 5379 (1998): 956–961, https://doi.org/10.1126/science.281.5379.956.

[27] X. H. Wu, C. R. Elsass, A. Abare, et al., “Structural Origin of V-Defects and Correlation With Localized Excitonic Centers in InGaN/GaN Multiple Quantum Wells,” Applied Physics Letters 72, no. 6 (1998): 692–694, https://doi.org/10.1063/1.120844.

[28] S. Zhou, X. Liu, H. Yan, et al., “The Effect of Nanometre-Scale V-Pits on Electronic and Optical Properties and Efficiency Droop of GaN-Based Green Light-Emitting Diodes,” Scientific Reports 8, no. 1 (2018): 11053, https://doi.org/10.1038/s41598-018-29440-4.

[29] R. Yapparov, T. Tak, J. Ewing, et al., “Carrier Diffusion in Long Wavelength InGaN Quantum Well LEDs After Injection through V-Defects,” Applied Physics Letters 125, no. 3 (2024): 031108, https://doi.org/10.1063/5.0215336.

[30] R. Loganathan, K. Prabakaran, S. Pradeep, S. Surender, S. Singh, and K. Baskar, “Influence of TMIn Flow Rate on Structural and Optical Quality of AlInGaN/GaN Epilayers Grown by MOCVD,” Journal of Alloys and Compounds 656 (2016): 640–646, https://doi.org/10.1016/j.jallcom.2015.10.019.

[31] Z. Pan, Z. Chen, H. Zhang, et al., “Isolated Red Quantum Wells With Strain Relaxation Induced by V-Pits and Trench Structures,” Optics Express 32, no. 24 (2024): 43184, https://doi.org/10.1364/OE.542926.

[32] S. Liu, D. Li, C. Lai, et al., “Impacts of the Area-Ratios of V-Pit for the Optoelectronic Performance of Green Micro-LEDs,” Journal of Alloys and Compounds 1010 (2025): 178100, https://doi.org/10.1016/j.jallcom.2024.178100.

[33] M. H. Zoellner, G. A. Chahine, L. Lahourcade, et al., “Correlation of Optical, Structural, and Compositional Properties With V-Pit Distribution in InGaN/GaN Multiquantum Wells,” ACS Applied Materials & Interfaces 11, no. 25 (2019): 22834–22839, https://doi.org/10.1021/acsami.9b04431.

[34] Q. Feng, L. Liu, Y. Zhang, et al., “Mechanism of V-Shaped Pits on Promoting Hole Injection in the InGaN MQWs: First-Principles Investigation,” ACS Omega 9, no. 6 (2024): 7163–7172, https://doi.org/10.1021/acsomega.3c09221.

[35] S. Marcinkevičius, T. Tak, Y. C. Chow, et al., “Dynamics of Carrier Injection Through V-Defects in Long Wavelength GaN LEDs,” Applied Physics Letters 124, no. 18 (2024): 181108, https://doi.org/10.1063/5.0206357.

[36] J. J. Ewing, C. Lynsky, M. S. Wong, et al., “High External Quantum Efficiency (6.5%) InGaN V-Defect LEDs at 600 nm on Patterned Sapphire Substrates,” Optics Express 31, no. 25 (2023): 41351, https://doi.org/10.1364/OE.503732.

[37] G. Wang, J. Huang, Y. Wang, et al., “Growth and Characterization of Micro-LED Based on GaN Substrate,” Optics Express 32, no. 18 (2024): 31463, https://doi.org/10.1364/OE.529771.

[38] D.-H. Kim, Y. S. Park, D. Kang, K. K. Kim, T. Y. Seong, and H. Amano, “Combined Effects of V Pits and Chip Size on the Electrical and Optical Properties of Green InGaN-Based Light-Emitting Diodes,” Journal of Alloys and Compounds 796 (2019): 146–152, https://doi.org/10.1016/j.jallcom.2019.05.070.

[39] 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,” Physical Review Letters 95, no. 12 (2005): 127402, https://doi.org/10.1103/PhysRevLett.95.127402.

[40] A. Hospodková, F. Hájek, T. Hubáček, et al., “Electron Transport Properties in High Electron Mobility Transistor Structures Improved by V-Pit Formation on the AlGaN/GaN Interface,” ACS Applied Materials & Interfaces 15, no. 15 (2023): 19646–19652, https://doi.org/10.1021/acsami.3c00799.

[41] S.-W. Chen, H. Li, C.-J. Chang, and T.-C. Lu, “Effects of Nanoscale V-Shaped Pits on GaN-Based Light Emitting Diodes,” Materials 10, no. 2 (2017): 113, https://doi.org/10.3390/ma10020113.

[42] C.-Y. Chang, H. Li, Y.-T. Shih, and T.-C. Lu, “Manipulation of Nanoscale V-Pits to Optimize Internal Quantum Efficiency of InGaN Multiple Quantum Wells,” Applied Physics Letters 106, no. 9 (2015): 091104, https://doi.org/10.1063/1.4914116.

[43] C. Xu, C. Zheng, X. Wu, et al., “Effects of V-Pits Covering Layer Position on the Optoelectronic Performance of InGaN Green LEDs,” Journal of Semiconductors 40, no. 5 (2019): 052801, https://doi.org/10.1088/1674-4926/40/5/052801.

[44] N. Sharma, P. Thomas, D. Tricker, and C. Humphreys, “Chemical Mapping and Formation of V-Defects in InGaN Multiple Quantum Wells,” Applied Physics Letters 77, no. 9 (2000): 1274–1276, https://doi.org/10.1063/1.1289904.

[45] J.-D. Gao, J.-L. Zhang, X. Zhu, et al., “Detailed Surface Analysis of V-Defects in GaN Films on Patterned Silicon(111) Substrates by Metal–Organic Chemical Vapour Deposition,” Journal of Applied Crystallography 52, no. 3 (2019): 637–642, https://doi.org/10.1107/S1600576719005521.

[46] Y. Liu, G. Wang, F. Feng, et al., “Low Dislocation Density Homoepitaxy Ultraviolet-A Micro-LEDs Scale Down to 3 μm,” IEEE Electron Device Letters 45, no. 4 (2024): 641–644, https://doi.org/10.1109/LED.2024.3368513.

[47] J. Bläsing, A. Reiher, A. Dadgar, A. Diez, and A. Krost, “The Origin of Stress Reduction by Low-Temperature AlN Interlayers,” Applied Physics Letters 81, no. 15 (2002): 2722–2724, https://doi.org/10.1063/1.1512331.

[48] Y. Cao, Q. Lv, T. Yang, et al., “Effect of EBL Thickness on the Performance of AlGaN Deep Ultraviolet Light-Emitting Diodes With Polarization-Induced Doping Hole Injection Layer,” Micro Nanostruct 175 (2023): 207489, https://doi.org/10.1016/j.micrna.2022.207489.

[49] C. K. Li, C. K. Wu, C. C. Hsu, et al., “3D Numerical Modeling of the Carrier Transport and Radiative Efficiency for InGaN/GaN Light Emitting Diodes With V-Shaped Pits,” AIP Advances 6, no. 5 (2016): 055208, https://doi.org/10.1063/1.4950771.

[50] L. Wang, C. Lu, J. Lu, et al., “Influence of Carrier Screening and Band Filling Effects on Efficiency Droop of InGaN Light Emitting Diodes,” Optics Express 19, no. 15 (2011): 14182–14187, https://doi.org/10.1364/OE.19.014182.

[51] S. Lai, C. Lai, S. Li, et al., “Green InGaN/GaN Multiple-Quantum-Wells With Pre-Layer for High-Efficiency Mini-LEDs,” IEEE Electron Device Letters 44, no. 6 (2023): 907–910, https://doi.org/10.1109/led.2023.3264983.

[52] M.-C. Shen, W. Guo, J. Chen, et al., “Improve Characteristics of GaN-Based Green Mini-LEDs With Double Dielectric Sidewall Passivation,” Physica Scripta 98, no. 11 (2023): 115524, https://doi.org/10.1088/1402-4896/acfb4d.

[53] T. Gong, Y. Yang, T. Xuan, et al., “Local Light Field Control Enables Efficient Quantum Dot Color Conversion Films for Mini-LED Backlit Displays,” Laser & Photonics Reviews 18, no. 10 (2024): 2301097, https://doi.org/10.1002/lpor.202301097.

[54] T. Xuan, S. Guo, W. Bai, T. Zhou, L. Wang, and R. J. Xie, “Ultrastable and Highly Efficient Green-Emitting Perovskite Quantum Dot Composites for Mini-LED Displays or Backlights,” Nano Energy 95 (2022): 107003, https://doi.org/10.1016/j.nanoen.2022.107003.

[55] J. Zhang, J. Wang, L. Cai, et al., “Fine-Tuning Crystal Structures of Lead Bromide Perovskite Nanocrystals Through Trace Cadmium(II) Doping for Efficient Color-Saturated Green LEDs,” Angewandte Chemie, International Edition in English 63, no. 26 (2024): e202403996, https://doi.org/10.1002/anie.202403996.

[56] J. Du, S. Liu, Z. Song, and Q. Liu, “All-Inorganic Green Synthesis of Small-Sized and Efficient K₂SiF₆:Mn⁴⁺ Phosphor for Mini-LED Displays,” ACS Applied Materials & Interfaces 15, no. 46 (2023): 53738–53745, https://doi.org/10.1021/acsami.3c13038.

[57] E. L. Routh, M. Abdelhamid, P. C. Colter, A. J. Bonner, N. A. El-Masry, and S. M. Bedair, “Reduction of V-Pit Density and Depth in InGaN Semibulk Templates and Improved LED Performance With Insertion of High Temperature Semibulk Layers,” Semiconductor Science and Technology 37, no. 7 (2022): 075003, https://doi.org/10.1088/1361-6641/ac6d01.

[58] R. C. White, M. Khoury, F. Wu, et al., “MOCVD Growth of Thick V-Pit-Free InGaN Films on Semi-Relaxed InGaN Substrates,” Semiconductor Science and Technology 36, no. 1 (2020): 015011, https://doi.org/10.1088/1361-6641/abc51c.

[59] K. S. Son, D. G. Kim, H. K. Cho, K. Lee, and K. Park, “Formation of V-Shaped Pits in GaN Thin Films Grown on High Temperature GaN,” Journal of Crystal Growth 261, no. 1 (2004): 50–54, https://doi.org/10.1016/j.jcrysgro.2003.08.075.

[60] M. S. Kumar, Y. S. Lee, J. Y. Park, S. Chung, C. H. Hong, and E. K. Suh, “Surface Morphological Studies of Green InGaN/GaN Multi-Quantum Wells Grown by Using MOCVD,” Materials Chemistry and Physics 113, no. 1 (2009): 192–195, https://doi.org/10.1016/j.matchemphys.2008.07.068.

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