Improved growth rates and purity of basic ammonothermal GaN

Abstract Improvements to the experimental setup for the basic ammonothermal growth of GaN and the introduction of a silver capsule into the autoclave have yielded an ultrahigh purity (UHP) growth environment with reproducible external wall temperature profiles to within the error of the thermocouples (type K with special limits of error (SLE), ±2.5 °C). 40 basic ammonothermal growth runs were performed on hydride vapor phase epitaxy (HVPE) GaN seed crystals with different crystal orientations to optimize the growth system. Due to the UHP growth environment, transition metal impurities in the GaN crystals were reduced to less than 1×10 17  cm −3 and oxygen impurity concentrations were comparable to those of the polycrystalline HVPE GaN source material (1×10 19  cm −3 ). Total growth rates improved to 344±30 μm/day for c -plane growth and 46±2 μm/day for m -plane growth. The crystal quality, as measured by the full width at half maximum (FWHM) of the ω-rocking curve using X-ray diffraction (ω-XRC), was comparable to that of the seed crystal, except for Ga-face growth on c -plane oriented seeds due to poor nucleation and cracking in thick growth layers due to strain originating from the HVPE seed crystals. The difference in total system pressure profiles during growth runs using autoclaves with and without a silver capsule was analyzed and the pressure drop due to outward diffusion of hydrogen during growth was modeled.

[1]  K. Fujito,et al.  Bulk GaN crystals grown by HVPE , 2009 .

[2]  S. Chichibu,et al.  Enhanced growth rate for ammonothermal gallium nitride crystal growth using ammonium iodide mineralizer , 2012 .

[3]  A. Baiker,et al.  Formation and thermal stability of copper and nickel nitrides , 1984 .

[4]  M. Ikeda,et al.  High-Power (over 100 mW) Green Laser Diodes on Semipolar {2021} GaN Substrates Operating at Wavelengths beyond 530 nm , 2012 .

[5]  S. Porowski.  Growth and properties of single crystalline GaN substrates and homoepitaxial layers , 1997 .

[6]  Xing Wu,et al.  Bulk GaN single crystals: growth conditions by flux method , 2003 .

[7]  D. S. Kamber,et al.  Evaluation of GaN substrates grown in supercritical basic ammonia , 2009 .

[8]  Shinichi Tanaka,et al.  High optical polarization ratio from semipolar (202¯1¯) blue-green InGaN/GaN light-emitting diodes , 2011 .

[9]  Tadao Hashimoto,et al.  Development of GaN wafers for solid-state lighting via the ammonothermal method , 2012 .

[10]  O. Shimomura,et al.  Congruent melting of gallium nitride at 6 GPa and its application to single-crystal growth , 2003, Nature materials.

[11]  Jan Van herle,et al.  Ammonia as a fuel in solid oxide fuel cells , 2003 .

[12]  J. Misiewicz,et al.  Ammonothermal GaN substrates: Growth accomplishments and applications , 2011 .

[13]  Y. Mori,et al.  Growth of bulk GaN crystal by Na flux method under various conditions , 2012 .

[14]  Michael A. Mastro,et al.  Seeded growth of GaN single crystals from solution at near atmospheric pressure , 2008 .

[15]  Extremely high current density over 1000 A/cm2 operation in m-plane GaN small size LEDs with low efficiency droop and method for controlling radiation pattern and polarization , 2012, 2012 International Electron Devices Meeting.

[16]  K. Katayama,et al.  531 nm Green Lasing of InGaN Based Laser Diodes on Semi-Polar {202̄1} Free-Standing GaN Substrates , 2009 .

[17]  J. Karpinski,et al.  Equilibrium pressure of N2 over GaN and high pressure solution growth of GaN , 1984 .

[18]  I. Chou.  Permeability of precious metals to hydrogen at 2 kb total pressure and elevated temperatures , 1986 .

[19]  D. Bliss,et al.  Ammonothermal growth of GaN crystals in alkaline solutions , 2006 .

[20]  M. Callahan,et al.  Ammonothermal Synthesis of III-Nitride Crystals , 2006 .

[21]  Jacqueline Akhavan,et al.  The chemistry of explosives , 1998 .

[22]  M. J. Suscavage,et al.  Ammonothermal growth of high-quality GaN crystals on HVPE template seeds , 2011 .

[23]  E. Shanley,et al.  The chemistry and free energy of formation of silver nitride , 1991 .

[24]  Masahiko Shimada,et al.  Preparation of GaN single crystals using a Na flux , 1997 .

[25]  S. Denbaars,et al.  High-Power Blue-Violet Semipolar (202̄1̄) InGaN/GaN Light-Emitting Diodes with Low Efficiency Droop at 200 A/cm2 , 2011 .

[26]  M. Leszczynski,et al.  The influence of lattice parameter variation on microstructure of GaN single crystals , 2005 .

[27]  M. Kamińska,et al.  GaN SYNTHESIS BY AMMONOTHERMAL METHOD , 1995 .

[28]  D. S. Kamber,et al.  Plane Dependent Growth of GaN in Supercritical Basic Ammonia , 2008 .