Ammonothermal Synthesis of III-Nitride Crystals

Abstract

Ammonothermal synthesis of nitrides is reviewed, with an emphasis on gallium and aluminum nitrides due to their important applications as direct wide band gap semiconductors. Since the crystallization process of nitrides involves the formation of some intermediate compounds during ammonothermal synthesis where a mineralizer is used, some ternary amides and ammoniates of aluminum and gallium with alkali metals or halides are also reviewed briefly. The ammonothermal crystallization of GaN and AlN bulk crystals, which is analogous to the hydrothermal growth of oxides, is introduced. Retrograde solubility, mineralizers, pressure-temperature-volume-concentration (PTVC) relations, phase relations, and transport growth of GaN in alkaline solutions are discussed in detail. Recent progress of GaN single-crystal growth by the ammonothermal technique is reported. We have grown GaN bulk single crystals up to 10 mm 2 by 1-mm thick. Issues such as ammonia breakdown, impurity incorporation, and scale-up of the ammonothermal growth of III-nitrides and perspectives on the method are also discussed.

Chemistry of Ammonothermal Synthesis

“…high capacity optical storage in CD-ROMs), in light emitting diodes, high electron mobility transistors and other devices [34,43]. The band gap for the group III nitrides decreases with increasing atomic weight of the metal constituent: AlN E g = 6.2 eV at 295 K [199], GaN E g = 3.39 eV [198] and InN E g = 0.7-0.8 eV [200,201].…”

“…If the substrate shows tilt boundaries, even if it is a native substrate but grown itself on a foreign substrate, the tilt boundaries will appear in the grown material, too [10,[37][38][39][40][41][42]. High quality of the substrate is very important, since it allows the production of more devices per substrate and devices made of low-defect-density GaN or AlN promise longer working periods at higher power without breakdown [43]. Solvothermal methods in general are known for their reliable and scalable process, which permits the efficient growth of a great number of crystals within one synthesis, e.g., 1400 quartz crystals, 1700 g each [36,44].…”

Growth and characterization of bulk GaN single crystals by basic ammonothermal method

“…inset 참조) [9]. 암모노써멀 성장 시스템에서 암모니아의 양이 감소함에 따라, 암모니아에 용해된 GaN species의 농도 증가는 궁극적으로 낮은 품질의 결정 및 과도한 양 의 이종 핵생성을 형성하는 성장 조건을 야기한다.…”

Ammonothermal Synthesis of Alkali‐Alkaline Earth Metal and Alkali‐Rare Earth Metal Carbodiimides: K5–xMx(CN2)2+x(HCN2)1–x(M= Sr, Eu) and Na4.32Sr0.68(CN2)2.68(HCN2)0.32

“…[27] (6) 104.96 (9) The FT-IR spectra of K 4.40 Eu 0.60 (CN 2 ) 2.60 (HCN 2 ) 0.40 ( Figure S1 and Table S1, Supporting Information) show analog vibrational bands as explained for K 4.16 Sr 0.84 (CN 2 ) 2.84 (HCN 2 ) 0. 16 . EDX measurements were carried out to determine the atomic ratio of K and Sr or Eu, respectively.…”