Patterned Sapphire Substrates for III-Nitride Epitaxial Growth
Natsuko Omiya*,†, Hideo Aida*, Yutaka Kimura*, Yuki Kawamata*, Seong-Woo Kim*, and Michio Uneda**
*Namiki Precision Jewel Co. Ltd.
3-8-22 Shinden, Adachi-ku, Tokyo 123-8511, Japan
**Kanazawa Institute of Technology, Nonoichi, Japan
GaN-based light emitting diodes (LEDs) were epitaxially grown on patterned sapphire substrates (PSSs) to investigate the effectiveness of PSSs for improving the internal quantum efficiency (IQE) and light extraction efficiency (LEE) of the LEDs. Using X-ray diffraction (XRD) and light output measurements, it was observed that the PSSs improved the crystal quality of the LED films and enhanced the LED light intensity. Based on these experimental results, we discuss whether the enhanced light intensity can be attributed to improvements in the IQE or the LEE. The contribution of the IQE improvement to the light intensity was estimated through a comparison of the calculated light emitting area of the LED chip and the measured light output. As a result, it was revealed that the IQE improvement is not the main cause of the increase in the light intensity, indicating that the PSSs mainly improve the LEE. A comparison of the calculated number of bumps on the PSSs and the measured light output of the LEDs suggests that an increase in the number of bumps could affect the improvement in the LEE.
-  H. Amano, M. Kito, K. Hiramatsu, and I. Akasaki, “P-Type Conduction in Mg-Doped GaN Treated with Low-Energy Electron Beam Irradiation (LEEBI),” Jpn. J. Appl. Phys., Vol.28, L2112, 1989.
-  S. Nakamura, “GaN Growth Using GaN Buffer Layer,” Jpn. J. Appl. Phys., Vol.30, Part 2, 10A, L1705, 1991.
-  S. W. Kim, H. Aida, and T. Suzuki, “Effect of Substrate Mis-Orientation on GaN Thin Films Grown by MOCVD Under Different Carrier Gas Condition,” Phys. Stat. Sol. (c), Vol.2, Issue 7, pp. 2170-2173, 2005.
-  S. W. Kim, H. Aida, and T. Suzuki, “The Effect of a Slight Mis-Orientation Angle of C-Plane Sapphire Substrate on Surface and Crystal Quality of MOCVD Grown GaN Thin Films,” Phys. Stat. Sol. (c), Vol.1, Issue 10, pp. 2483-2486, 2004.
-  S. W. Kim, H. Aida, and T. Suzuki, “Influence of Mis-Orientation of C-plane Sapphire Substrate on the Early Stages of MOCVD Growth of GaN Thin Films,” Mater. Res. Soc. Symp. Proc. Vol.831, E3.40, 2011.
-  H. Aida, S. W. Kim, K. Sunakawa, N. Aota, K. Koyama, M. Takeuchi, and T. Suzuki, “III-nitride Epitaxy on Atomically Controlled Surface of Sapphire Substrate with Slight Misorientation,” Jpn. J. Appl. Phys., Vol.51, 25502, 2012.
-  H. Aida, D. S. Lee, M. Belousov, and K. Sunakawa, “Effect of Initial Bow of Sapphire Substrate on Substrate Curvature during InGaN Growth Stage of Light Emitting Diode Epitaxy,” Jpn. J. Appl. Phys., Vol.51, 12102, 2012.
-  K. Tadatomo, H. Okagawa, Y. Ohuchi, T. Tsunekawa, Y. Imada, M. Kato, and T. Taguchi, “High Output Power InGaN Ultraviolet Light-Emitting Diodes Fabricated on Patterned Substrates Using Metalorganic Vapor Phase Epitaxy,” Jpn. J. Appl. Phys., Vol.40, L583, 2001.
-  C. Huh, K. S. Lee, E. J. Kang, and S. J. Park, “Improved Light-Output and Electrical Performance of InGaN-Based Light-Emitting Diode by Microroughening of the p-GaN Surface,” J. Appl. Phys., Vol.93, 9383, 2003.
-  W. K. Wang, D. S. Wuu, S. H. Lin, S. Y. Huang, P. Han, and R. H. Horng, “Characteristics of Flip-Chip InGaN-Based Light-Emitting Diodes on Patterned Sapphire Substrates,” Jpn. J. Appl. Phys., Vol.45, 3430, 2006.
-  S. M. Jeong, S. Kissinger, D. W. Kim, S. J. Lee, J. S. Kim, H. K. Ahn, and C. R. Lee, “Characteristic Enhancement of the Blue LED Chip by the Growth and Fabrication on Patterned Sapphire (0 0 0 1) Substrate,” J. Cryst. Growth, Vol.312, Issue 2, pp. 258-262, 2010.
-  S. H. Park, H. Jeon, Y. J. Sung, and G. Y. Yeom, “Refractive Sapphire Microlenses Fabricated by Chlorine-Based Inductively Coupled Plasma Etching,” Appl. Opt., Vol.40, Issue 22, pp. 3698-3702, 2001.
-  C. H. Jeong, D. W. Kim, K. N. Kim, and G. Y. Yeom, “A Study of Sapphire Etching Characteristics Using BCl3-Based Inductively Coupled Plasmas,” Jpn. J. Appl. Phys., Vol.41, 6206, 2002.
-  D. W. Kim, C. H. Jeong, K. N. Kim, H. Y. Lee, H. S. Kim, Y. J. Sung, and G. Y. Yeom, “High Rate Sapphire (Al2O3) Etching in Inductively Coupled Plasmas Using Axial External Magnetic Field,” Thin Solid Films, Vol.435, pp. 242-246, 2003.
-  D. W. Kim, C. H. Jeong, K. N. Kim, H. Y. Lee, H. S. Kim, and G. Y. Yeom, “High Rate Sapphire Etching Using BCl3-Based Inductively Coupled Plasma,” J. Korean. Phys. Soc., Vol.42, S795, 2003.
-  J. Cho, H. Kim, J. W. Lee, S. Yoon, C. Sone, Y. Park, and E. Yoon, “Simulation and Fabrication of Highly Efficient InGaN-Based LEDs with Corrugated Interface Substrate,” Phys. Status Solidi C, Vol.2, Issue 7, pp. 2874-2877, 2005.
-  J. H. Lee, J. T. Oh, J. S. Park, J. W. Kim, Y. C. Kim, J. W. Lee, and H. K. Cho, “Improvement of Luminous Intensity of InGaN Light Emitting Diodes Grown on Hemispherical Patterned Sapphire,” Phys. Status Solidi C, Vol.3, Issue 6, pp. 2169-2173, 2006.
-  C. C. Wang, H. Ku, C. C. Liu, K. K. Chong, C. I. Hung, Y. H. Wang, and M. P. Houng, “Enhancement of the Light Output Performance for GaN-Based Light-Emitting Diodes by Bottom Pillar Structure,” Appl. Phys. Lett., Vol.91, 121109, 2007.
-  J. H. Cheng, Y. S. Wu, W. C. Liao, and B. W. Lin, “Improved Crystal Quality and Performance of GaN-Based Light-Emitting Diodes by Decreasing the Slanted Angle of Patterned Sapphire,” Appl. Phys. Lett., Vol.96, 051109, 2010.
-  T. Fujii, Y. Gao, R. Sharma, E. L. Hu, S. P. DenBaars, and S. Nakamura, “Increase in the Extraction Efficiency of GaN-Based Light-Emitting Diodes Via Surface Roughening,” Appl. Phys. Lett., Vol.84, 855, 2004.
-  W. K. Wang, S. Y. Huang, S. H. Huang, K. S. Wen, D. S. Wuu, and R. H. Horng, “Fabrication and Efficiency Improvement of Micropillar InGaN/Cu Light-Emitting Diodes with Vertical Electrodes,” Appl. Phys. Lett., Vol.88, 181113, 2006.
-  K. Ban, J. Yamamoto, K. Takeda, K. Ide, M. Iwaya, T. Takeuchi, S. Kamiyama, I. Akasaki, and H. Amano, “Internal Quantum Efficiency of Whole-Composition-Range AlGaN Multiquantum Wells,” Appl. Phys. Express, Vol.4, 052101, 2011.
-  Q. Dai, M. F. Schubert, M. H. Kim, J. K. Kim, E. F. Schubert, D. D. Koleske, M. H. Crawford, S. R. Lee, A. J. Fischer, G. Thaler, and M. A. Banas, “Internal Quantum Efficiency and Nonradiative Recombination Coefficient of GaInN/GaN Multiple Quantum Wells with Different Dislocation Densities,” Appl. Phys. Lett., Vol.94, 111109, 2009.
-  C. C. Kao, H. C. Kuo, K. F. Yeh, J. T. Chu, W. L. Peng, H. W. Huang, T. C. Lu, and S. C. Wang, “Light-output Enhancement of Nano-Roughened GaN Laser Lift-Off Light-Emitting Diodes Formed by ICP Dry Etching,” IEEE Photon. Technol. Lett., Vol.19, Issue 11, pp. 849-851, 2007.
-  T. Metzger, R. Höpler, E. Born, O. Ambacher, M. Stutzmann, R. Stömmer, M. Schuster, H. Göbel, S. Christiansen, M. Albrecht, and H. P. Strunk, “Defect Structure of Epitaxial GaN Films Determined by Transmission Electron Microscopy and Triple-Axis X-Ray Diffractometry,” Philos. Mag. A, Vol.77, Issue 4, pp. 1013-1025, 1998.
-  H. Heinke, V. Kirchner, S. Einfeldt, and D. Hommel, “X-Ray Diffraction Analysis of the Defect Structure in Epitaxial GaN,” Appl. Phys. Lett., Vol.77, 2145, 2000.
-  A. Sakai, H. Sunakawa, and A. Usui, “Defect Structure in Selectively Grown GaN Films with Low Threading Dislocation Density,” Appl. Phys. Lett., Vol.71, 2259, 1997.
-  T. Sugahara, H. Sato, M. Hao, Y. Naoi, S. Kurai, S. Tottori, K. Yamashita, K. Nishino, L. T. Romano, and S. Sakai, “Direct Evidence that Dislocations are Non-Radiative Recombination Centers in GaN,” Jpn. J. Appl. Phys., Vol.37, L398, 1998.
-  J. J. Chen, Y. K. Su, C. L. Lin, S. M. Chen, W. L. Li, and C. C. Kao, “Enhanced Output Power of GaN-Based LEDs With Nano-Patterned Sapphire Substrates,” IEEE Photon. Technol. Lett., Vol.20, Issue 13, pp. 1193-1195, 2008.
-  M. S. Shur and R. Gaska, “Deep-Ultraviolet Light-Emitting Diodes,” IEEE Trans. Electron Devices, Vol.57, Issue 1, pp. 12-25, 2010.
-  M. Imura, K. Nakano, N. Fujimoto, N. Okada, K. Balakrishnan, M. Iwaya, S. Kamiyama, H. Amano, I. Akasaki, T. Noro, T. Takagi, and A. Bandoh, “Dislocations in AlN Epilayers Grown on Sapphire Substrate by High-Temperature Metal-Organic Vapor Phase Epitaxy,” Jpn. J. Appl. Phys., Vol.46, 1458, 2007.
This article is published under a Creative Commons Attribution-NoDerivatives 4.0 Internationa License.