Enhanced hole transport in AlGaN deep ultraviolet light-emitting diodes using a double-sided step graded superlattice electron blocking layer

Abstract

In this paper, deep ultraviolet AlGaN light-emitting diodes (LEDs) with a novel double-sided step graded superlattice (DSGS) electron blocking layer (EBL) instead of a conventional EBL have been proposed for ∼ 254 n m wavelength emission. The enhanced carrier transport in the DSGS structure results in reduced electron leakage into the p -region, improved hole activation and hole injection, and enhanced output power and external quantum efficiency. The calculations show that output power of the DSGS structure is ∼ 3.56 times higher and electron leakage is ∼ 12 times lower, compared to the conventional structure. Moreover, the efficiency droop at 60 mA in the DSGS LED was found to be ∼ 9.1 % , which is ∼ 4.5 times lower than the regular LED structure.

Enhancing Efficiency of AlGaN Ultraviolet‐B Light‐Emitting Diodes with Graded p‐AlGaN Hole Injection Layer

“…To improve the hole activation and hole injection into the active region, different band‐engineered superlattice (SL) structures have been adopted; i.e., single‐/double‐step‐graded SL structure in the EBL [ 11,12 ] and SL hole injection layer (HIL). [ 13 ] A SL structure has been demonstrated for improved hole activation efficiency by reducing the Mg activation energy.…”

Improved Performance of Electron Blocking Layer Free AlGaN Deep Ultraviolet Light-Emitting Diodes Using Graded Staircase Barriers

“…Moreover, as the EBL is Al-rich, Mg doping efficiency gets affected because of high acceptor activation energy, compensation by nitrogen vacancies, increased hole scattering, and limited acceptor solubility [ 6 ]. To address the above-mentioned problems, QW or EBL is re-engineered using different approaches [ 7 , 8 , 9 , 10 , 11 ]. This could partially reduce the challenges generated by the integration of the EBL, but it is always desired to improve the LED efficiency by eliminating the EBL layer.…”

Improved Performance of GaN-Based Ultraviolet LEDs With Electron Blocking Layers Composed of Double-Peak p-Type Al x Ga1−x N/GaN Superlattice Layers

“…Ultraviolet light-emitting diodes (UV-LEDs) have generated intensive interest due to their many advantages compared to conventional UV mercury lamps, as well as their wide applicability in numerous applications such as in water purification, medical treatment, analytical sensing and high-density optical storage devices [1][2][3][4]. Among the many developed UV LED technologies, GaN-based UV LEDs have attracted considerable attention owing to their direct bandgap, high electron saturation mobility, and large optical power output density [5,6].…”

“…All of these efficiencies are responsible for the low EQE of AlGaN UV LEDs [9]. This issue has been addressed by applying a p-type AlGaN electron blocking layer (EBL) to prevent the electron overflow, which has resulted in increased external quantum efficiency (EQE) and optical power output [2,10]. Other studies have applied p-type AlxGa1−xN layers with stepgraded values of x as EBLs in GaN-based LEDs.…”

“…Analyses of LED devices with different AlGaN-based EBL materials have demonstrated that the Al component provides an important contribution toward their electron overflow suppression effect due to the resulting polarization field in the EBL [16]. Efforts to improve the hole injection and confine electron overflow in UV LEDs have led to the application of double-side step-graded SL-EBL (DSGS-EBL) structures [2]. Here, the DSGS-EBL structure was demonstrated to increase efficiency and optical power output due to the formation of effective conduction band barrier height, which prevented electron overflow into the p-type region.…”