An excellent hybrid III‐nitride/nanocrystal nanohole light‐emitting diode (h‐LED) has been developed utilizing nonradiative resonant energy transfer (NRET) between violet/blue emitting InGaN/GaN multiple quantum wells (MQWs) and various wavelength emitting nanocrystals (NCs) as color‐conversion mediums. InGaN/GaN MQWs are fabricated into nanoholes by soft nanoimprint lithography to minimize the separation between MQWs and NCs. A significant reduction in the decay lifetime of excitons in the MQWs of the hybrid structure has been observed as a result of the NRET from the nitride emitter to NCs. The NRET efficiency of the hybrid structures is obtained from the decay curves, as high as 80%. Moreover, a modified Förster formulation has exhibited that the exciton coupling distance in the hybrid structures is less than the Förster's radius, demonstrating a strong coupling between MQWs and NCs. Finally, based on a systemic optimization for white emission indexes, a series of hybrid ternary complementary color h‐LEDs have been demonstrated with a high color rendering index, up to 82, covering the white light emission at different correlated color temperatures ranging from 2629 to 6636 K, corresponding to warm white, natural white, and cold white.
A series of highly ordered c-plane InGaN/GaN elliptic nanorod (NR) arrays were fabricated by our developed soft UV-curing nanoimprint lithography on a wafer. The photoluminescence (PL) integral intensities of NR samples show a remarkable enhancement by a factor of up to two orders of magnitude compared with their corresponding as-grown samples at room temperature. The radiative recombination in NR samples is found to be greatly enhanced due to not only the suppressed non-radiative recombination but also the strain relaxation and optical waveguide effects. It is demonstrated that elliptic NR arrays improve the light extraction greatly and have polarized emission, both of which possibly result from the broken structure symmetry. Green NR light-emitting diodes have been finally realized, with good current-voltage performance and uniform luminescence.
Highly ordered c-plane InGaN/GaN elliptic nanorod (NR) and nano-grating (NG) arrays were fabricated by our developed soft UV-curing nanoimprint lithography on a wafer. The polarized photoluminescence emission from these elliptic NR and NG arrays has been investigated both theoretically and experimentally. Considerable in-plane optical anisotropy, with a polarization ratio of 15% and 71% and a peak shift of 5.2 meV and 28.1 meV, was discovered from these c-plane InGaN/GaN elliptic NR and NG arrays, respectively. The k·p perturbation theory was adopted to explore this situation, simulating the transitions from conduction subbands to valence subbands and their corresponding optical momentum matrix elements at/around Γ point under the in-plane asymmetric strain. The good agreements of observed and simulated results demonstrate that the in-plane strain asymmetry is the essential cause of the optical polarization in this case, revealing the great potential to utilize strain effect to control the polarization of InGaN/GaN nanostructures.
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