Details

Autor(en) / Beteiligte

• Bai, J.
• Wang, T.
• Li, H.D.
• Jiang, N.
• Sakai, S.

Titel

(0 0 0 1) oriented GaN epilayer grown on [formula omitted] sapphire by MOCVD

Ist Teil von

• Journal of crystal growth, 2001-09, Vol.231 (1), p.41-47

Ort / Verlag

Amsterdam: Elsevier B.V

Erscheinungsjahr

2001

Quelle

Elsevier Journal Backfiles on ScienceDirect (DFG Nationallizenzen)

Beschreibungen/Notizen

• Since the major advantage of (1 1 2 ̄ 0) sapphire substrate is the ability to easily form cleaved facets, which is important for the fabrication of edge-emitting lasers, it is meaningful to investigate the GaN epilayer grown on (1 1 2 ̄ 0) sapphire substrate. X-ray diffraction (XRD) measurement indicates that the GaN growth is still along (0 0 0 1) direction even on (1 1 2 ̄ 0) sapphire substrate. However, compared with the GaN grown on (0 0 0 1) sapphire substrate, the GaN layer on (1 1 2 ̄ 0) sapphire substrate shows a larger c-axis lattice constant and smaller a-axis lattice constant, which indicates that there exists an enhanced lattice-mismatch compared with the case on (0 0 0 1) sapphire substrate. The detailed XRD measurement indicates that the strain exerted on the GaN on (1 1 2 ̄ 0) sapphire substrate is increased by 0.03% compared with that on (0 0 0 1) sapphire substrate. Furthermore, the low-temperature photoluminescence indicates that the GaN on (1 1 2 ̄ 0) sapphire substrate shows a 4.5 meV blue-shift compared with the GaN on (0 0 0 1) sapphire substrate, which is in a good agreement with our calculation based on the lattice-mismatch induced strain model. A crystallographic depict is proposed for a good explanation of a GaN layer growth on (1 1 2 ̄ 0) sapphire substrate. By selective-area diffraction (SAD) and high-resolution transmission electron microscopy measurement (HREM), the in-plane orientation relationship is determined to be (1 1 2 ̄ 0) GaN ∥(1 1 ̄ 0 0) sapphire and (1 1 ̄ 0 0) GaN ∥(0 0 0 1) sapphire , which also shows that a larger lattice-mismatch between (0 0 0 1) GaN and (1 1 2 ̄ 0) sapphire substrate occurs and thus gives rise to an enhanced compressive strain. In turn, it supports our above discussion.