Enhanced the Optical Power of AlGaN-Based Deep Ultraviolet Light-Emitting Diode by Optimizing Mesa Sidewall Angle

Abstract

In this work, we propose and optimize the sidewalls for the mesa to enhance the optical power for AlGaN-based deep ultraviolet light-emitting diodes (LEDs). We obtain the mesa with the inclined sidewalls by conducting dry etching. The optical performance for LED devices with different inclination angles are tested by putting the integrated sphere on the sapphire side of the devices. The DUV LED with the optimal angle of 37.83°yields the 48% optical power enhancement at the current density of 35 A/cm 2 as compared with the reference device. The physical mechanism for the impact of the mesa inclination angle on the light extraction efficiency is also discussed both theoretically and experimentally. Then, we find that once the Al reflector is evaporated on the insulated silica dioxide that is coated on the sidewall of the mesa, the light extraction efficiency for the TM-polarized DUV photons and the optical power can be further improved.

Light Extraction Enhancement of InGaN Based Micro Light-Emitting Diodes with Concave-Convex Circular Composite Structure Sidewall

“…It is further proved that the concave-convex circular composite structure sidewalls achieve an improvement in micro-LED light efficiency without losing a large amount area of active region, on account of the TIR reduction. For further revealing the mechanism of concave-convex circular composite structure sidewall on light extraction, the propagation of transverse electric (TE) and transverse magnetic (TM) polarized blue photons with a radio of 1.8:1 were simulated by using finite-difference time-domain (FDTD) method [37][38][39]. The FDTD simulation model of the different sidewall structures and the corresponding simulated electric-magnetic field intensity distribution nearby the sidewalls are shown in the Figure 8.…”

Enhanced Performance of InGaN‐Based Blue LEDs Using an AlGaN/InGaN Super‐Lattice Last Quantum Barrier

“…After the growth and characterization of the epitaxial wafer, then we fabricated the 380 × 760 µm 2 LED chips by following the standard blue LED process . The EQE and optical power for all packaged chips are measured [see Figure ] by integrating sphere test system.…”

Progress in External Quantum Efficiency for III‐Nitride Based Deep Ultraviolet Light‐Emitting Diodes

“…Another design to enhance the LEE for the TM‐polarized light is to modulate the propagation direction of the beam, which can be achieved by adopting the inclined side wall reflector . The beam propagation can be tuned and the LEE for DUV LEDs can also be enhanced by using the inclined mesa . The optimized inclined angle for the mesa is found to be 37.83° according to the report by Chen et al Most recently, our group has further modified the inclined sidewall structure, such that we place the bottom metal mirror with air cavities in the adjacent mesas so that the TM‐polarized DUV photons can be less absorbed by the sidewall metal mirrors…”