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Valence band (VB) effective masses of nonpolar and semipolar nitride heterostructures were studied using k·p perturbation theory, with a particular focus on band mixing. When the absolute value of the energy separation of the topmost two VBs (|ΔE|) is sufficiently larger than the spin-orbit interaction (Δso), the mixing between these two VBs was negligible. This enabled us to calculate an analytical expression for VB mass expression. Under this condition, the effective mass of the top VB was reduced less than 10% along a certain direction, and less than 25% for an in-plane (x′y′-plane) average, compared to the c-plane case. When ΔE was comparable with Δso, however, the VB structure became isotropic due to band mixing. Consequently, the VB band structure approached that of the c-plane and optical polarization was suppressed. On the other hand, VB mass along the growth direction (z′) was always heavy, similar to that of the c-plane. However, the topmost two VBs had slightly different mass values along z′, which affected radiative properties of non-c-plane nitride quantum wells (less than 2 nm wide) through the difference in quantum confinement strengths. [ABSTRACT FROM AUTHOR]

A color synthesis based on InGaN/GaN quantum wells (QWs) grown on GaN microfacets formed by regrowth on SiO2 mask stripes is demonstrated. The microfacet structure is composed of (0001), (1122), and (1120) planes, and the InGaN well thickness and composition are spatially inhomogeneous due to the diffusion of the adatoms among the facets. These properties allow microfacet QWs, which, for example, emit yellow from the (0001) facet and blue from the (1122) facet, to be fabricated, of which the luminescence appears white due to the additive color mixing. Using a mask pattern that consists of regions with and without stripes, the emissions from the microfacet QWs and from planar QWs are synthesized to produce the desired apparent output colors. [ABSTRACT FROM AUTHOR]

Rainbow color luminescence from InxGa1-xN single quantum wells (SQWs) is achieved and almost covers the entire visible range when the layers are fabricated on {1122}facets with a few micron-width using a regrowth technique on striped GaN templates. These facets are tilted 56° with respect to the (0001)facets and border the (0001) and {1120} facets. The emission wavelength on the {1122} facets is redshifted from the {1120} side to (0001) side due to the variations of the In composition, which leads to the color contrast with the rainbow geometry. The temperature dependence of the photoluminescence intensity shows that the internal quantum efficiency at room temperature is 33% due to the very small internal electric fields and a small threading dislocation density compared to that in conventional (0001) InxGa1-xN SQWs. Since the emission efficiency does not show a noticeable emission wavelength dependence, this type of structure has potential as light-emitting devices with multiwavelengths that perform numerous color controllability such as pastel and white colors. [ABSTRACT FROM AUTHOR]