11:30 AM - 11:45 AM
▲ [26a-E203-10] Exploring Highly Transparent p-AlGaN Layer for 304nm-Band UVB LED via Engineering of nanoPSS and Photonic Crystal
Keywords:nanoPSS, AlGaN UVB LED, Photonic Crystal (PhC)
Recently, we investigated the influence of Al-graded p-type multi-quantum-barrier electron-blocking-layer (Al-grad p-MQB EBL) and Al-graded p-AlGaN hole source layer (HSL) on the generation and injection of 3D holes in the active region. A significant improvement in the experimental efficiency (EQE) and light output power of about 8.2% and 36 mW was noticed [1]. Also, a remarkable improvement in the efficiency (EQE) of up to 9.6% and light output power of 40 mW, even in the absence of photonic crystal (PhC)/nanoPSS, and resin-like lenses, is achieved on bare-wafer under continuous-wave operation at room temperature using highly reflective Ni/Al p-electrode. However, we can further enhance the light extraction efficiency (LEE) by exploiting a special design of PhC and nanoPSS [2] simultaneously in 304nm-Band UVB LED. In this work, FDTD simulation model for nanoPSS in the C-Sapphire as well as Reflecting PhC in the p-AlGaN Contact layer of pure AlGaN based UVB LED was investigated. The pitch (a), diameter (d) and height (h) were optimized for 304 nm emission wavelength. The Bragg`s condition was used, with m: order, neff: effective refractive index, λ: wavelength, and a: pitch, respectively. For nanoPSS (hole-shaped), the order m = 10, d = 596 nm, a = 746 nm, R/a =0.40, and height = 500 nm was found to be suitable. For PhC (hole-shaped), the order m = 3-4 with R/a =0.20-0.40, and height = 150 nm was found to be precious too. Consequently, the LEE was enhanced approximately to 140 % by using m: 3 and 4, respectively, in UVB LED, as shown in Fig. 1(B). References: [1] M. Ajmal Khan et al. “Achieving 9.6% Efficiency in 304 nm p-AlGaN UVB LED via Increasing the Holes Injection and Light Reflectance” Accepted in Scientific Reports (2022) of Springer Nature. [2] H. Ogiya et al. “Improvement of LED Luminance Efficiency by Sapphire Nano PSS Etching” CS MANTECH Conference, May 13th - 16th, 2013, New Orleans, Louisiana, USA.