Ultrahigh Degree of Optical Polarization above 80% in AlGaN-Based Deep-Ultraviolet LED with Moth-Eye Microstructure

Abstract

For the first time, an ultrahigh degree of optical polarization (DOP) of 81.8% in AlGaN-based deep ultraviolet LED (DUV-LED) operated at 286 nm has been experimentally demonstrated. The very high DOP was obtained by introducing the novel moth-eye microstructure fabricated on the backside of a sapphire substrate. Compared with conventional DUV-LED with a DOP of 64.7%, a significant 1.26-fold enhancement was obtained. It was worth mentioning that the DOP was accurately measured via self-built full spatial transverse electric (TE) and transverse magnetic (TM) mode light intensity test system, which was mainly composed of angle resolution bracket, Glan-Taylor prism, and spectrometer. For both TE and TM mode light, the extraction angle inside the semiconductor was extended from conventional (−26°, 26°), (−52°, −41°), (41°, 52°) to (−52°, 52°). Combined with finite difference time domain simulation, it was further confirmed that the novel moth-eye microstructure could notably weaken the total internal reflection at the sapphire/air interface and enlarge the light extraction angle. As a result, compared with the conventional one, DUV-LED with a moth-eye microstructure approximately doubled the light extraction efficiency.

Nanoantenna‐Enhanced Light‐Emitting Diodes: Fundamental and Recent Progress

“…[ 65,66 ] Another example is the helical traveling‐wave nanoantenna, which enables the tunable polarization control by the optical spin–orbit interaction. [ 67 ] There are also nanostructures such as the moth eye, [ 68 ] which could improve the degree of optical polarization and then double the LEE of LED.…”

Deep-ultraviolet integrated photonic and optoelectronic devices: A prospect of the hybridization of group III–nitrides, III–oxides, and two-dimensional materials

“…They were able to enhance the performance of 282 compared with conventional at sapphire substrate, by adopting NSL and wet etching mechanisms. In another report, Zhou et al demonstrated the effect of different sizes of cone-shaped-PSS on performance of UV LED emitting at 375 nm [446] . They noticed that TDDs are in a decreased trend associated with increasing pattern sizes and with the PSS filling factor.…”

“…In their design, a conventional Al x Ga 1-x N-based LED is modified into a UV LED structure by utilizing the following features: Fig. 16 shows a moth-eye micro-arrays which was fabricated on the back of sapphire platform to significantly increase the LEE by weakening the total internal reflection (TIR) [447] . Consequently, a high degree of optical polarization (DOP) of 81.8% is obtained for DUV LED utilizing moth-eye micro-arrays, compared to a standard DUV LED of DOP of 64.7%.…”

Multiple fields manipulation on nitride material structures in ultraviolet light-emitting diodes

“…However, light will be reflected at the interface between media and will be absorbed by p - or n -type layers and electrodes. For AlGaN, the total reflection angle is only 26° 42 , thereby resulting in extremely low LEE. On the other hand, AlGaN materials with high Al content have significant optical anisotropy.…”