Efficiency Improvement of Deep‐Ultraviolet Light Emitting Diodes with Gradient Electron Blocking Layers

Abstract

In this paper, a gradient electron blocking layer (GEBL) is introduced to improve efficiency of deep‐ultraviolet light‐emitting diodes (DUV‐LEDs). Various structures of DUV‐LEDs are simulated to determine the energy band diagram variation and carrier injection mechanism resulting from the insertion of the GEBL. The simulation results show the improved electron and hole transport behavior in AlGaN multi quantum wells (MQWs). Especially, the injection efficiency of holes is improved with the increasing number of GEBL steps, which lead to the enhancement of internal quantum efficiency (IQE). The DUV‐LED structures with GEBL are grown in a high‐temperature metal‐organic chemical vapor deposition (HT‐MOCVD) system. Electroluminescence (EL) spectra show that the emission intensity at a wavelength of 280 nm from a DUV‐LED with a 12‐steps EBL is about 2.3 times that from a DUV‐LED with a single EBL.

Enhanced Performance of AlGaN-Based Deep Ultraviolet Light-Emitting Diodes with Chirped Superlattice Electron Deceleration Layer

“…But only a few holes can be injected into the active region through the barrier in the valence band introduced by the EBL, and even less holes can cross the barriers of the active region and transport to the quantum wells near n-type layers because of low activation efficiency of the Mg dopant and small mobility of holes [21]. Various attempts have been made to improve electron and hole injection, such as hole barrier layer, specifically designed last barrier, EBL, and multiple quantum well structures [22–26]. Nevertheless, the performance of DUV LEDs is not substantially improved.…”

Influence of Quantum-Well Number and an AlN Electron Blocking Layer on the Electroluminescence Properties of AlGaN Deep Ultraviolet Light-Emitting Diodes

“…The influence of the EBL with different structures on the EL properties of DUV-LEDs has been investigated by many groups [25][26][27][28]. Generally, we used 1 nm i-AlN as an EBL to suppress the electron overflow [20].…”

“…Obviously, the suppression efficiency of electron overflow in LED D was better than in LED A. Furthermore, LED D showed advanced property compared to LED C. Correspondingly, the relative output power was increased significantly for LED D. The influence of the EBL with different structures on the EL properties of DUV-LEDs has been investigated by many groups [25][26][27][28]. Generally, we used 1 nm i-AlN as an EBL to suppress the electron overflow [20].…”

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

“…However, AlGaN based DUV LEDs are also influenced by the unbalanced carrier injection, such that the electron injection has to be enhanced . A direct method to suppress the electron leakage for DUV LEDs is to engineer the p‐EBL, for example, superlattice p‐EBL, p‐EBL with AlGaN insertion layer, p‐EBL with the graded AlN composition, superlattice last quantum barrier . Moreover, the electron concentration in the MQWs can be enhanced by proposing novel active region structure, for example, Si doped quantum barriers, grading the AlN composition for the AlGaN based quantum barriers, increasing the AlN composition for AlGaN based quantum barrier …”