MOVPE growth and characterization of a -plane AlGaN over the entire composition range

• Published in: Physica status solidi. PSS-RRL. Rapid research letters Vol. 4; no. 7; pp. 163 - 165
• Main Authors: Laskar, Masihhur R., Ganguli, Tapas, Rahman, A. A., Shah, A. P., Gokhale, M. R., Bhattacharya, Arnab
• Format: Journal Article
• Language: English
• Published: Berlin WILEY-VCH Verlag 01-07-2010; WILEY‐VCH Verlag; Wiley-VCH
• Subjects: AlGaN; Aluminum; Aluminum gallium nitrides; Anisotropy; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Diffraction; Distortion; Exact sciences and technology; III−V semiconductors; Materials science; Methods of deposition of films and coatings; film growth and epitaxy; MOCVD; Nucleation; Physics; Sapphire; Structure and morphology; thickness; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Thin film structure and morphology; Vapor phase epitaxy; Vapor phase epitaxy; growth from vapor phase; X-ray diffraction; Lattice distortion; X-ray diffraction; XRD; Lattice parameters; MOCVD; AlGaN; Hexagonal lattices; Anisotropy; Aluminium Gallium Nitrides Mixed; MOVPE method; Growth mechanism; III―V semiconductors; III-V semiconductors
• ISSN: 1862-6254; 1862-6270; 1862-6270
• DOI: 10.1002/pssr.201004091

We report the metal organic vapor phase epitaxy (MOVPE) growth and characterization of non‐polar (11$ \bar 2 $0) a ‐plane Alx Ga1–xN on (1$ \bar 1 $02) r ‐plane sapphire substrates over the entire composition range. Alx Ga1–xN samples with ∼0.8 μm thick layers and with x = 0, 0.18, 0.38, 0.46, 0.66, and 1.0 have been grown on r ‐plane sapphire substrates. The layer quality can be improved by using a 3‐stage AlN nucleation layer and appropriate V/III ratio switching following nucleation. All a ‐plane AlGaN epilayers show an anisotropic in‐plane mosaicity, strongly influenced by Al incorporation and growth conditions. Careful lattice parameter measurements show anisotropic in‐plane strain that results in an orthorhombic distortion of the hexagonal unit cell, making Al composition determination from X‐ray diffraction difficult. In general lower Al incorporation is seen in a ‐plane epilayers compared to c ‐plane samples grown under the same conditions. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
This Letter reports the metal organic vapor phase epitaxy (MOVPE) growth and characterization of non‐polar (11$ \bar 2 $0) a ‐plane AlxGa1–xN on (1$ \bar 1 $02) r‐plane sapphire substrates over the entire Al composition range. Careful lattice parameter measurements show an anisotropic in‐plane strain that leads to an orthorhombic distortion of the hexagonal unit cell. The authors outline a method for determining the Al composition for such distorted structures. They find that the epilayer mosaicity is strongly influenced by Al content and growth conditions.