研究目的
Investigating the size-dependent characteristics of blue and green InGaN microLEDs down to 1 μm in diameter, focusing on external quantum efficiency (EQE) trends.
研究成果
The study successfully fabricated InGaN microLEDs down to 1 μm in diameter and analyzed their size-dependent EQE trends. Green wavelength devices showed less susceptibility to efficiency reductions with decreasing size, attributed to smaller surface recombination velocities due to enhanced carrier localization. This results in higher EQE values for green devices below 10 μm diameters despite lower bulk efficiencies.
研究不足
The study is limited by the fabrication challenges at sizes below 5 μm and the convoluted effects of processing on sidewall recombination studies. Additionally, the optical measurement setup may underestimate EQE values compared to integrating sphere measurements.
1:Experimental Design and Method Selection:
The study utilized standard semiconductor processing techniques, including lithography and etching, to fabricate InGaN microLEDs with diameters ranging from 1 to 30 μm.
2:Sample Selection and Data Sources:
Commercial c-plane epitaxial material grown on sapphire was used for fabricating blue and green wavelength devices.
3:List of Experimental Equipment and Materials:
Equipment included a scanning electron microscope (SEM) for imaging, a monochromator (Horiba Jovin Yvon iHR320) with a Synapse CCD detector for EL spectra measurement, and a fiber-coupled blackbody source (Ocean Optics LS-1-CAL) for radiometric calibrations.
4:Experimental Procedures and Operational Workflow:
Devices were fabricated using a self-aligned undercut structure to form dielectric apertures without precise alignments. Optical measurements were conducted on-chip, collecting light transmitted through the sapphire substrate.
5:Data Analysis Methods:
EQE was calculated from optical power, mean wavelength of the EL spectrum, and current density using the provided equations.
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