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26 February 2016 Designing optically pumped InGaN quantum wells with long wavelength emission for a phosphor-free device with polarized white-light emission
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Abstract
We report a semipolar III-nitride device in which an electrically injected blue light emitting diode optically pumps monolithic long wavelength emitting quantum wells (QWs) to create polarized white light. We have demonstrated an initial device with emission peaks at 440 nm and 560 nm from the electrically injected and optically pumped QWs, respectively. By tuning the ratio of blue to yellow, white light was measured with a polarization ratio of 0.40. High indium content InGaN is required for long wavelength emission but is difficult to achieve because it requires low growth temperatures and has a large lattice mismatch with GaN. This device design incorporates optically pumped QWs for long wavelength emission because they offer advantages over using electrically injected QWs. Optically pumped QWs do not have to be confined within a p-n junction, and carrier transport is not a concern. Thus, thick GaN barriers can be incorporated between multiple InGaN QWs to manage stress. Optically pumping long wavelength emitting QWs also eliminates high temperature steps that degrade high indium content InGaN but are required when growing p-GaN for an LED structure. Additionally, by eliminating electrical injection, the doping profile can instead be engineered to affect the emission wavelength. We discuss ongoing work focused on improving polarized white light emission by optimizing the optically pumped QWs. We consider the effects of growth conditions, including: trimethylindium (TMI) flow rate, InGaN growth rate, and growth temperature. We also examine the effects of epitaxial design, including: QW width, number of QWs, and doping.
© (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Stacy J. Kowsz, Christopher D. Pynn, Feng Wu, Robert M. Farrell, James S. Speck, Steven P. DenBaars, and Shuji Nakamura "Designing optically pumped InGaN quantum wells with long wavelength emission for a phosphor-free device with polarized white-light emission", Proc. SPIE 9748, Gallium Nitride Materials and Devices XI, 97481Z (26 February 2016); https://doi.org/10.1117/12.2209661
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