On the Hole Injection for III-Nitride Based Deep Ultraviolet Light-Emitting Diodes

Abstract

The hole injection is one of the bottlenecks that strongly hinder the quantum efficiency and the optical power for deep ultraviolet light-emitting diodes (DUV LEDs) with the emission wavelength smaller than 360 nm. The hole injection efficiency for DUV LEDs is co-affected by the p-type ohmic contact, the p-type hole injection layer, the p-type electron blocking layer and the multiple quantum wells. In this report, we review a large diversity of advances that are currently adopted to increase the hole injection efficiency for DUV LEDs. Moreover, by disclosing the underlying device physics, the design strategies that we can follow have also been suggested to improve the hole injection for DUV LEDs.

Enhancement of Light Extraction Efficiency for InGaN/GaN Light-Emitting Diodes Using Silver Nanoparticle Embedded ZnO Thin Films

“…Because gallium-nitride (GaN)-based blue light-emitting diodes (LEDs) have the inherent advantages of a wide bandgap in the green to ultraviolet range, a relatively long lifetime, and low energy consumption, they have received intensive and extensive investigation. InGaN/GaN LEDs with a high light output intensity and low power consumption have been widely applied to products such as solid-state lighting, backlight units for liquid crystal displays, car headlights, traffic lights, and full-color displays [1,2,3,4]. More recently, GaN-based LEDs and solid-state lighting were widely used as transmitting devices in the visible light communication (VLC) system, which has the characteristics of high-speed light communication with low transmission loss, the absence of electromagnetic interference, and license and high security [5,6,7].…”

“…The IQE is affected by the concentration of defects, amount of overflow carriers, and spreading area of injection current in the active region. To obtain a modern InGaN/GaN LED with a high IQE, various device structures, such as a designed active region including double-heterostructures and multiple quantum wells (MQWs), the insertion of an electron-blocking layer, and an expanded current-spreading layer, have been investigated [2]. To date, IQEs of higher than 80% have been achieved for InGaN/GaN LEDs because of the rapid development of growth methods and technologies [8,9,10].…”

Nearly Efficiency-Droop-Free AlGaN-Based Ultraviolet Light-Emitting Diodes with a Specifically Designed Superlattice p-Type Electron Blocking Layer for High Mg Doping Efficiency

“…Ultraviolet beams in the wavelength regime of 200 nm~280 nm have found potential applications in water purification system [ 1 , 2 ]. Considering the low DC driving voltage and the more compatibility with the water purification system, AlGaN-based deep ultraviolet light-emitting diodes (DUV LEDs) are selected as the excellent candidate.…”

“…Therefore, the EQE improvement is smaller than 20% and efficiency droop is still obvious even if the GaN/AlGaN superlattice p-EBL is adopted for blue LEDs. DUV LEDs employ Al-rich p-EBLs, giving rise to an even more challenging hole injection issue [ 1 ]. To solve the Al-rich p-EBL-caused hole blocking effect, superlattice p-EBL is also suggested for DUV LEDs, e.g., AlInGaN/AlGaN superlattice p-EBL [ 22 ] and AlGaN/AlGaN superlattice p-EBL [ 23 ].…”

Recent Advances on III‐Nitride Nanowire Light Emitters on Foreign Substrates – Toward Flexible Photonics

“…Though the success of GaN epilayer technologies in blue/blue–green spectral range, their extension to ultraviolet (UV) and near‐infrared (NIR) has been lagging behind, by and large, due to the high defect/dislocation densities and poor p‐type doping as more In and Al are incorporated . Moreover, these photonic devices are mostly built on sapphire, bulk GaN, and SiC substrates, which are rigid, and cannot meet the growing demand for new functionalities, for example, wearable devices, which require flexible electronic and photonic device components. Although using mechanical polishing, mechanical peeling off, dry techniques such as laser lift‐off, and epitaxial lift‐off such as selective wet etching of sacrificial layer or entire substrate, these rigid substrates can be removed and III‐nitride epilayers can be transferred to flexible substrates.…”