InGaN/GaN multiple quantum well (MQW) structures suffer from a high amount of compressive strain in the InGaN wells and the accompanied piezoelectric field resulting in both a blue shift in emission and a reduction of emission intensity. We report the growth of InxGa1−xN/GaN “strain-balanced” multiple quantum wells (SBMQWs) grown on thick InyGa1−yN templates for x > y by metal organic chemical vapor deposition. SBMQWs consist of alternating layers of InxGa1−xN wells and GaN barriers under compressive and tensile stress, respectively, which have been lattice matched to a thick InyGa1−yN template. Growth of the InyGa1−yN template is also detailed in order to achieve thick, relaxed InyGa1−yN grown on GaN without the presence of V-grooves. When compared to conventional InxGa1−xN/GaN MQWs grown on GaN, the SBMQW structures exhibit longer wavelength emission and higher emission intensity for the same InN mole fraction due to a reduction in the well strain and piezoelectric field. By matching the average lattice constant of the MQW active region to the lattice constant of the InyGa1−yN template, essentially an infinite number of periods can be grown using the SBMQW growth method without relaxation-related effects. SBMQWs can be utilized to achieve longer wavelength emission in light emitting diodes without the use of excess indium and can be advantageous in addressing the “green gap.”

Thick, high-quality InGaN layers can be used as templates for quantum well strain reduction in light-emitting diodes and as optical absorption layers in solar cell structures. Current InGaN growth technology, however, is primarily limited by V-pit formation and non-uniform indium composition. We report the growth and characterization of thick, strain-relaxed In y Ga 12y N layers, with 0.08 £ y £ 0.11, by metal organic chemical vapor deposition using the semibulk approach, which consists in periodic insertion of 2-nm GaN interlayers into the bulk In y Ga 12y N structure; these are then spike-annealed at 1000°C. Photoluminescence, x-ray diffraction, and scanning electron and atomic force microscopy revealed that the semibulk In y Ga 12y N had optical and electrical properties superior to those of conventional bulk In y Ga 12y N grown at the same temperature. Homogeneous indium content and substantial reduction of V-pit density were observed for the semibulk In y Ga 12y N films, even when grown above the critical layer thickness. Double-crystal x-ray diffraction rocking curves also revealed a one order of magnitude reduction of screw dislocation density in the semibulk In y Ga 12y N film compared with the bulk In y Ga 12y N film.

We demonstrate gallium nitride (GaN) nanowires formation by controlling the selective and anisotropic etching of N-polar GaN in hot phosphoric acid. Nanowires of ∼109/cm,2 total height of ∼400 nm, and diameters of 170–200 nm were obtained. These nanowires have both non-polar {11¯00}/ {112¯0} and semi-polar {1011¯} facets. X–Ray Diffraction characterization shows that screw dislocations are primarily responsible for preferential etching to create nanowires. Indium gallium nitride multi-quantum wells (MQWs) grown on these GaN nanowires showed a blue shift in peak emission wavelength of photoluminescence spectra, and full width at half maximum decreased relative to MQWs grown on planar N-polar GaN, respectively.

We demonstrate a metalorganic chemical vapor deposition growth approach for inverting N-polar to Ga-polar GaN by using a thin inversion layer grown with high Mg flux. The introduction of this inversion layer allowed us to grow p-GaN films on N-polar GaN thin film. We have studied the dependence of hole concentration, surface morphology, and degree of polarity inversion for the inverted Ga-polar surface on the thickness of the inversion layer. We then use this approach to grow a light emitting diode structure which has the MQW active region grown on the advantageous N-polar surface and the p-layer grown on the inverted Ga-polar surface.