The roles of low-temperature buffer layer for thick GaN growth on sapphire

• Published in: Journal of crystal growth Vol. 310; no. 5; pp. 920 - 923
• Main Authors: Lee, H.J., Lee, S.W., Goto, H., Lee, Hyo-Jong, Ha, Jun-Seok, Fujii, K., Cho, M.W., Yao, T., Hong, S.K.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 01.03.2008; Elsevier
• Subjects: A3. Hydride vapor-phase epitaxy; B1. Gallium nitride; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Materials science; Methods of deposition of films and coatings; film growth and epitaxy; Physics; Structure and morphology; thickness; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Theory and models of film growth; Thin film structure and morphology; Vapor phase epitaxy; growth from vapor phase; 81.10.Bk; 81.15.Kk; B1. Gallium nitride; 81.05.Ea; A3. Hydride vapor-phase epitaxy; Buffer layer; Temperature dependence; Crystal defects; Thick films; VPE; A3. Hydride vapor-phase epitaxy; Bl. Gallium nitride; XRD; Gallium nitride; Heat treatments; Voids; Ammonium chloride; Thin films; Interfaces; Temperature effects; Sapphire; Rocking curve; Growth mechanism; Stress effects; III-V semiconductors; Crystal structure; 81.05.Ea; 81.10.Bk; 81.15.Kk
• ISSN: 0022-0248; 1873-5002
• DOI: 10.1016/j.jcrysgro.2007.11.105

Thick GaN films were grown on two different low-temperature GaN (LT-GaN)-buffer layers, i.e., one- and two-step LT-GaN buffer, by hydride vapor-phase epitaxy (HVPE). NH 4Cl layer was included in two-step LT-GaN, which was evaluated by X-ray diffraction patterns. Many voids were observed at the interface for both samples. We will discuss the mechanism of void formation for both samples. The full-width at half-maximum (FWHM) values of (0 0 0 2) ω-rocking curves were 390 and 440 arcsec for 200-μm-thick GaN on one- and two-step LT-GaN, respectively. The 200-μm-thick high-temperature GaN (HT-GaN) film on two-step LT-GaN was self-separated without any cracks after cooling down. NH 4Cl layer included into two-step LT-GaN buffer was effectively contributed to the voids formation and self-separation in realizing a stress-free free-standing GaN (FS-GaN) substrate.