Optics & Laser Technology 152 (2022) 108156 0030-3992/© 2022 Published by Elsevier Ltd. Performance enhancement of AlGaN deep-ultraviolet laser diode using compositional Al-grading of Si-doped layers Muhammad Nawaz Sharif a, * , M. Ajmal Khan b , Qamar. Wali c , Ilkay Demir d , Fang Wang a, e, * , Yuhuai Liu a, e, f, * a National Center for International Joint Research of Electronic Materials and Systems, International Joint-Laboratory of Electronic Materials and Systems of Henan Province, and Henan Key Laboratory of Laser and Opto-electric Information Technology, School of Information Engineering, Zhengzhou University, Zhengzhou, Henan 450001, PR China b Riken Cluster for Pioneering Research, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan c School of Applied Sciences & Humanities, National University of Technology Islamabad, Pakistan d Nanophotonics Research and Application Center, Department of Nanotechnology Engineering, Sivas Cumhuriyet University, 58140 Sivas, Turkey e Zhengzhou Way Do Electronics Co. Ltd., Zhengzhou, Henan 450001, PR China f Institute of Materials and Systems for Sustainability, Nagoya University, Nagoya, Aichi-ken 464-8601, Japan A R T I C L E INFO Keywords: Deep-ultraviolet laser diode Compositional grading of AlGaN Cladding layer Waveguide layer ABSTRACT Achieving high threshold current density and high optical confnement are big challenges in the realization of high-performance aluminum gallium nitride (AlGaN)-based deep-ultraviolet (DUV) laser diode (LD). In this work, compositional Al-grading of AlGaN layers is used to increase the optical confnement factor (OCF), carrier injection effciency, gain, and emission power of the DUV LD. Compositional grading of waveguides (WGs) layer, electron blocking layer (EBL), and cladding layers (CLs) demonstrated that the device characteristic can be improved. By using compositional Al-grading of AlGaN p-WG, EBL, p-CL along with n-WG and n-CL, 17.4% OCF, 94.4 mW emission power, and 1369 m 1 gain at 267 nm peak emission wavelength are achieved. These im- provements are attributed to the reduced threshold current density as well as using better optical confnement scheme in the DUV LD. 1. Introduction AlGaN-based ultraviolet emitters (light-emitting diode, laser diode) have attracted much attention due to widespread applications in the feld of water, air, purifcation, medical equipment sterilization, medi- cine, proteins identifcation, horticultural applications, bio-chemical sensing, biotechnology, and surfaces disinfection [1–4]. The require- ment of ultraviolet emitters against viruses and bacteria inactivation is increasing rapidly [5]. The recent global pandemic caused by novel the Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV-2) even further raised these expectations. Human being in nature has always coexisted with various infectious diseases and germs since the inception of life. The spread of the SARS-CoV-2 virus has not only damage to human lives but also damage to the world economy and people’s life- styles. Therefore, controlling of all infectious diseases is a global issue for human society now and in the far future too. To inactivate viruses and germs using harmless ultraviolet-C (UVC) light technology is inev- itable for a better food to eat, water to drink, and air to breath. Ac- cording to international ultraviolet associations (IUVA), DUV light sources with emission wavelengths from 250 to 280 nm were found to be effective in the inactivation of SARS-CoV2. A study proved that a virus stuffed at a concentration of 5 × 10 6 TCID 50 /mL can be completely inactivated by using a dose of 292 mJ/cm 2 of DUV light source for 9 min at an emission wavelength of 254 nm [6]. Toyoda Gosei Ltd. develops an AlGaN-based DUV light-emitting diode (LEDs) module emitting at 275 nm with irradiation power of 2.6 mW/cm 2 and can inactivate 99.99% SARS-CoV-2 sample within 5 s [7]. AlGaN is considered a suitable ma- terial for the development of ultraviolet emitters due to its direct wide bandgap tunability from 210 to 370 nm which covers the whole ultra- violet spectrum [8,9]. AlGaN-based emitters have many advantages over * Corresponding authors at: National Center for International Joint Research of Electronic Materials and Systems, International Joint-Laboratory of Electronic Materials and Systems of Henan Province, and Henan Key Laboratory of Laser and Opto-electric Information Technology, School of Information Engineering, Zhengzhou University, Zhengzhou, Henan 450001, PR China (F. Wang, Y. Liu). E-mail addresses: Nawazkhattak@gs.zzu.edu.cn (M.N. Sharif), iefwang@zzu.edu.cn (F. Wang), ieyhliu@zzu.edu.cn (Y. Liu). Contents lists available at ScienceDirect Optics and Laser Technology journal homepage: www.elsevier.com/locate/optlastec https://doi.org/10.1016/j.optlastec.2022.108156 Received 7 October 2021; Received in revised form 20 March 2022; Accepted 6 April 2022