High internal quantum efficiency ultraviolet to green luminescence peaks from pseudomorphic m-plane Al1−xInxN epilayers grown on a low defect density m-plane freestanding GaN substrate

• Published in: Journal of applied physics Vol. 116; no. 21
• Main Authors: Chichibu, S F, Hazu, K, Furusawa, K, Ishikawa, Y, Onuma, T, Ohtomo, T, Ikeda, H, Fujito, K
• Format: Journal Article
• Language: English
• Published: Melville American Institute of Physics 07.12.2014
• Subjects: Applied physics; Axial stress; Density; Epitaxial growth; Gallium nitrides; Luminescence; Metalorganic chemical vapor deposition; Plane stress; Quantum efficiency; Substrates
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.4902315

Structural and optical qualities of half-a-μm-thick m-plane Al1−xInxN epilayers grown by metalorganic vapor phase epitaxy were remarkably improved via coherent growth on a low defect density m-plane freestanding GaN substrate prepared by hydride vapor phase epitaxy. All the epilayers unexceptionally suffer from uniaxial or biaxial anisotropic in-plane stress. However, full-width at half-maximum values of the x-ray ω-rocking curves were nearly unchanged as the underlayer values being 80 ∼ 150 arc sec for (101¯0) and (101¯2) diffractions with both ⟨0001⟩ and ⟨112¯0⟩ azimuths, as long as pseudomorphic structure was maintained. Such Al1−xInxN epilayers commonly exhibited a broad but predominant luminescence peak in ultraviolet (x ≤ 0.14) to green (x = 0.30) wavelengths. Its equivalent value of the internal quantum efficiency at room temperature was as high as 67% for x = 0.14 and 44% for x = 0.30. Because its high-energy cutoff commonly converged with the bandgap energy, the emission peak is assigned to originate from the extended near-band-edge states with strong carrier localization.