Improvement in Light Output of Ultraviolet Light-Emitting Diodes with Patterned Double-Layer ITO by Laser Direct Writing

Abstract

A patterned double-layer indium-tin oxide (ITO), including the first unpatterned ITO layer serving as current spreading and the second patterned ITO layer serving as light extracting, was applied to obtain uniform current spreading and high light extraction efficiency (LEE) of GaN-based ultraviolet (UV) light-emitting diodes (LEDs). Periodic pinhole patterns were formed on the second ITO layer by laser direct writing to increase the LEE of UV LED. Effects of interval of pinhole patterns on optical and electrical properties of UV LED with patterned double-layer ITO were studied by numerical simulations and experimental investigations. Due to scattering out of waveguided light trapped inside the GaN film, LEE of UV LED with patterned double-layer ITO was improved as compared to UV LED with planar double-layer ITO. As interval of pinhole patterns decreased, the light output power (LOP) of UV LED with patterned double-layer ITO increased. In addition, UV LED with patterned double-layer ITO exhibited a slight degradation of current spreading as compared to the UV LED with a planar double-layer ITO. The forward voltage of UV LED with patterned double-layer ITO increased as the interval of pinhole patterns decreased.

Enhanced Light Extraction of Flip-Chip Mini-LEDs with Prism-Structured Sidewall

“…Tremendous efforts have been done to improve the efficiency of GaN-based LEDs, which can be principally divided into two categories: improving the crystal quality of epilayer [6,7,8,9,10] and boosting the light extraction efficiency (LEE) [11,12,13,14,15]. Since mini-LEDs are obtained from the identical epilayer as broad-area LEDs, the fruitful methods for high crystal quality epilayer are universal in fabrication of the two kinds of LEDs.…”

Highly Deep Ultraviolet–Transparent h-BN Film Deposited on an Al0.7Ga0.3N Template by Low-Temperature Radio-Frequency Sputtering

“…A DUV-transparent h-BN layer would act as a multifunctional layer; it is a current spreading layer for current spreading to the entire chip, an effective electron blocking layer that prevents the electron from overflowing to the p-regime, and a good ohmic contact layer to form low contact resistance to metal. Specifically, the high transmittance of h-BN enables the application of various techniques based on multiple reflections to extract light efficiently from the DUV optical devices [37][38][39]. for both hole injection and electron blocking with respect to Al0.7Ga0.3N [15].…”

Optoelectronic Nanodevices

“…The continuous nanostructure-based applications development provides the confidence to significantly improve existing products and to explore the design of materials and devices with novel functionalities [9][10][11]. Reproduced with permission from [15]; (e) typical J-V curves of a ternary organic solar cells (OSC) device and schematic representation of charge transfer between the active layer materials. Reproduced with permission from [16]; (f) schematic representation of a two-dimensional (2D) [15]; (e) typical J-V curves of a ternary organic solar cells (OSC) device and schematic representation of charge transfer between the active layer materials.…”

“…Reproduced with permission from [15]; (e) typical J-V curves of a ternary organic solar cells (OSC) device and schematic representation of charge transfer between the active layer materials. Reproduced with permission from [16]; (f) schematic representation of a two-dimensional (2D) [15]; (e) typical J-V curves of a ternary organic solar cells (OSC) device and schematic representation of charge transfer between the active layer materials. Reproduced with permission from [16]; (f) schematic representation of a two-dimensional (2D) perovskite platelet phototransistor.…”

“…In that way, the complex TCE exhibited very high transmittance values at 365 nm and extremely low specific contact resistance, upon annealing. The combination of two single ITO layers is demonstrated by Zhao et al [15] for GaN-based UV LEDs, in order to improve light extraction efficiency (LEE) and to reach low-resistance ohmic contact with the layer of p-GaN. The concept was implemented using laser direct writing and was further supported by numerical simulations.…”