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The growth mechanisms during metalorganic vapor phase epitaxy of InGaN quantum wells (QWs) on three-dimensional GaN microfacet structures composed of (0001) and {11-22} planes were investigated. The cross section of the microfacet structures formed by regrowth was changed from triangle to trapezoid, depending on the mask geometries for the regrowth. The emission peak wavelength of the (0001) microfacet QWs was always longer than that of the {11-22} microfacet QWs, and the difference is smaller than in planar (0001) and {11-22} QWs. To clarify this observation, the local thicknesses of constituent InN and GaN on the GaN microfacets were estimated. Using a formula derived from the diffusion equation, the distribution of the local thickness is fitted to estimate the apparent diffusion lengths, λ. For Ga, λ was fitted to be 5.2 μm on (0001) and 3.1 μm on {11-22}, while for In, λ was 2.7 μm on (0001) and 1.6 μm on {11-22}. This suggests that the degree of migration of adatoms depends on both facets and atoms, which may cause the facet-dependent In compositions and lead to multiwavelength emission from microfacet InGaN QWs. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) |
