Visible-Color-Tunable Light-Emitting Diodes
ABSTRACT Visible-color-tunable light-emitting diodes (LEDs) with electroluminescent color that changes continuously from red to blue by adjusting the external electric bias are fabricated using multifacetted GaN nanorods with anisotropically formed 3D InGaN multiple-quantum wells. Monolithically integrated red, green, and blue LEDs on a single substrate, operating at a fixed drive current, are also demonstrated for inorganic full-color LED display applications.
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ABSTRACT: A solar cell based on a hybrid nanowire–film architecture consisting of a vertically aligned array of InGaN/GaN multi-quantum well core–shell nanowires which are electrically connected by a coalesced p-InGaN canopy layer is demonstrated. This unique hybrid structure allows for standard planar device processing, solving a key challenge with nanowire device integration, while enabling various advantages by the nanowire absorbing region such as higher indium composition InGaN layers by elastic strain relief, more efficient carrier collection in thinner layers, and enhanced light trapping from nano-scale optical index changes. This hybrid structure is fabricated into working solar cells exhibiting photoresponse out to 2.1 eV and short-circuit current densities of ~1 mA cm(-2) under 1 sun AM1.5G. This proof-of-concept nanowire-based device demonstrates a route forward for high-efficiency III-nitride solar cells.Nanotechnology 04/2012; 23(19):194007. DOI:10.1088/0957-4484/23/19/194007 · 3.67 Impact Factor
Article: Strain relaxation in GaN nanopillars[Show abstract] [Hide abstract]
ABSTRACT: In this work, we demonstrate the direct measurement of the strain state at the surface of nanostructures by in-plane X-ray diffraction. GaN tapered nanopillars have been fabricated by dry etching of a highly strained epilayer. The strain of the surface as function of pillar height shows an exponential relaxation which can be described by a single relaxation parameter. Additionally, we have simulated the strain relaxation and distribution of nanopillars. The impact of the pillar geometry on the strain relaxation has been discussed. In agreement with the measurements, an exponential relaxation of the strain is observed.Applied Physics Letters 12/2012; 101(25). DOI:10.1063/1.4772481 · 3.52 Impact Factor
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ABSTRACT: Highly ordered, position-controlled gallium nitride (GaN) nanowire based multiple-quantum-wells (MQWs) core–shell architecture arrays are synthesized by metalorganic chemical vapor deposition (MOCVD). We investigate the possibility of using GaN nanowire arrays as a basal template for the growth of InxGa1−xN/GaN MQWs. The MQWs on three different crystal facets (c-, m-, and semipolar-plane) of GaN nanowire exhibit dissimilar structural properties. The structural characteristics of InGaN/GaN core–shell arrays are inspected by cross-sectional high-resolution transmission electron microscopy (HR-TEM). We also investigate the optical properties of MQW core–shell structure nanoarrays. The luminescent characteristics of InGaN/GaN core–shell structure arrays are determined by photoluminescence (PL) and cathodoluminescence (CL) measurements. The monochromatic CL images clearly show the light emission behavior of InGaN/GaN MQW coaxial structure. Two distinguishable light emission peaks were observed in the GaN nanowire based core–shell structure. The characteristic of light emission mainly depends on the properties of MQWs, which are generated from different crystal facets of GaN. In addition, the light emission intensity shows different behaviors depending on the area of the GaN nanowire m-plane. The results of this study suggest that GaN nanowire arrays can be used as a good alternative basal template for next-generation light-emitting diodes (LEDs).Nano Energy 11/2014; 11. DOI:10.1016/j.nanoen.2014.11.003 · 10.21 Impact Factor