研究目的
Investigating the full-spatial decomposition of TE/TM mode in AlGaN-based DUV-LEDs to enhance light extraction efficiency.
研究成果
The full-spatial decomposition of TE/TM mode in AlGaN-based DUV-LEDs was experimentally investigated, showing that roughened sidewall could notably weaken the total internal reflection at sapphire/air interface and help photons escape out of MQWs. The LEE of DUV-LED was increased by 1.36 times through the twice laser stealth dicing in sapphire thickness ~200 um. The self-built light intensity test system can accurately measure the polarization characteristics and is useful to characterize the anisotropic extraction behavior of polarized sources.
研究不足
The actual dicing depth would differ from the design value, which could affect the roughness and effective roughening region. The true refractive index of the sapphire sidewall after laser-scribing cannot be determined, making it impossible to accurately calculate the value of four areas under different cutting conditions.
1：Experimental Design and Method Selection:
The study introduced a self-built light intensity test system composed of an angle resolution bracket, Glan-Taylor prism, and spectrometer to investigate the TE/TM mode light intensity of AlGaN-based DUV-LEDs.
2：Sample Selection and Data Sources:
AlGaN-based DUV-LEDs were grown on c-sapphire substrate by metalorganic chemical vapor deposition (MOCVD). The wafer was divided into four pieces for different conditions of laser stealth dicing.
3：List of Experimental Equipment and Materials:
The laser system is a 1064 nm semiconductor pumped picosecond laser. Optical microscopy (OLYMPUS BX51) was used to perform the morphologies of sapphire sidewall microstructure.
4：Experimental Procedures and Operational Workflow:
The DUV-LED chips with varying conditions of laser stealth dicing were obtained after chip splitting and tape expander. Finally, the DUV-LED chips were packaged on ceramic substrate.
5：Data Analysis Methods:
The full spatial TE/TM mode light intensity test system with a Glan-Taylor prism placed between DUV-LED fixed on an angle resolution bracket and spectrometer was used to measure the light intensity at different wavelengths.
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