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

Jiahui Hu,Yi Zhang,Changqing Chen,Qian Chen,Jun Zhang,Maocheng Shan,Hanling Long,Shida Du,Huixue Zhang,Jiangnan Dai

doi:10.1186/s11671-019-3201-x

Abstract

AlGaN-based deep ultraviolet (DUV) light-emitting diodes (LEDs) suffer from electron overflow and insufficient hole injection. In this paper, novel DUV LED structures with superlattice electron deceleration layer (SEDL) is proposed to decelerate the electrons injected to the active region and improve radiative recombination. The effects of several chirped SEDLs on the performance of DUV LEDs have been studied experimentally and numerically. The DUV LEDs have been grown by metal-organic chemical vapor deposition (MOCVD) and fabricated into 762 × 762 μm2 chips, exhibiting single peak emission at 275 nm. The external quantum efficiency of 3.43% and operating voltage of 6.4 V are measured at a forward current of 40 mA, indicating that the wall-plug efficiency is 2.41% of the DUV LEDs with ascending Al-content chirped SEDL. The mechanism responsible for this improvement is investigated by theoretical simulations. The lifetime of the DUV LED with ascending Al-content chirped SEDL is measured to be over 10,000 h at L50, due to the carrier injection promotion.

Highlights

In recent years, AlGaN-based deep ultraviolet (DUV) light-emitting diodes (LEDs), whose spectra ascribed to UVB (320 nm–280 nm) and UVC (280 nm–100 nm), have attracted much attention because of their applications in plant lighting, phototherapy, water purification, and air and surface sterilization [1–6]
The results show that the X-ray rocking curves (XRC) full width at half maximum (FWHM) and threading dislocation density (TDD) of four samples are nearly the same, indicating that the crystalline quality is not the main reason for the device performance improvement
The results indicate that chirped superlattice electron deceleration layer (SEDL) are able to equilibrate electron and hole injection into the active region, which promotes the radiative recombination in the first few quantum wells near n-type layers

Summary

Introduction

AlGaN-based deep ultraviolet (DUV) light-emitting diodes (LEDs), whose spectra ascribed to UVB (320 nm–280 nm) and UVC (280 nm–100 nm), have attracted much attention because of their applications in plant lighting, phototherapy, water purification, and air and surface sterilization [1–6]. The light output power (LOP) of the state-of-the-art AlGaNbased DUV LEDs drops significantly as the light emission wavelength gets shorter [7, 8]. Those DUV LEDs suffer from low internal quantum efficiency (IQE), light extraction efficiency (LEE), and carrier injection efficiency (CIE) [9–13]. 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, designed last barrier, EBL, and multiple quantum well structures [22–26]. The performance of DUV LEDs is not substantially improved

Methods

Results

Conclusion