InGaN/GaN self-organized quantum dot green light emitting diodes with reduced efficiency droop

Zhang, Meng; Bhattacharya, Pallab; Guo, Wei

doi:doi:10.1063/1.3460921

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Optically induced fast wavelength modulation in a quantum cascade laser

An optically induced fast wavelength shift is demonstrated in a standard middle infrared (MIR) quantum cascade laser (QCL) by illuminating the front facet with a femtosecond (fs) near infrared (NIR) laser, allowing fast optical frequency modulation (FM) for free space optical communication (FSOC) and FM spectroscopy. Using an etalon as a narrow band-pass wavelength filter, the wavelength modulation (WM) was clearly observed at frequencies up to 1.67 GHz. This approach can also be used for wavel...

Long exciton spin relaxation in coupled quantum wells

Spatially indirect excitons in a coupled quantum well structure were studied by means of polarization and time-resolved photoluminescence. A strong degree of circular polarization (>50%) in emission was achieved when the excitation energy was tuned into resonance with the direct exciton state. The indirect transition remained polarized several tens of nanoseconds after the pumping laser pulse, demonstrating directly a very long relaxation time of exciton spin. The observed spin relaxation ti...

High density (2–5×10¹⁰ cm⁻²) self-organized InGaN/GaN quantum dots were grown by plasma-assisted molecular beam epitaxy. Room temperature photoluminescence shows that the quantum dots have strong emission ranging from 430 to 524 nm. The internal quantum efficiency of dots emitting at 500 nm was determined to be 32% by temperature dependent photoluminescence measurements. A recombination lifetime of 0.57 ns is derived from time resolved photoluminescence measurements. These superior optical properties are attributed to a small piezoelectric field in the quantum dots. Light emitting diodes fabricated with the InGaN/GaN quantum dots and emitting at λ = 524 nm demonstrate a small blueshift with current injection and reduced efficiency droop.

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KEYWORDS and PACS

Keywords

gallium compounds, III-V semiconductors, indium compounds, light emitting diodes, photoluminescence, piezoelectric semiconductors, semiconductor quantum dots, spectral line shift, surface recombination, time resolved spectra, wide band gap semiconductors

PACS

81.07.Ta

Quantum dots
82.53.Kp

Coherent spectroscopy of atoms and molecules
81.40.Tv

Optical and dielectric properties related to treatment conditions

ARTICLE DATA

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http://dx.doi.org/10.1063/1.3460921

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0003-6951 (print)

1077-3118 (online)

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American Institute of Physics

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