Materials Science and Engineering B 263 (2021) 114879 Available online 21 October 2020 0921-5107/© 2020 Elsevier B.V. All rights reserved. Inclination of screw dislocations on the performance of homoepitaxial GaN based UV photodetectors Neha Aggarwal a, b , Shibin Krishna a, b , Lalit Goswami a , Govind Gupta a, b, * a CSIR – National Physical Laboratory (CSIR-NPL), Dr K. S. Krishnan Road, New Delhi 110012, India b Academy of Scientifc & Innovative Research, CSIR-HRDC Campus, Ghaziabad, Uttar Pradesh 201002, India A R T I C L E INFO Keywords: Dislocation-assisted Homoepitaxy Screw dislocations Photodetector Photoresponsivity ABSTRACT We analyze the dislocation-assisted charge carrier transport and effective photocurrent generation in the pho- todetection devices. Specifcally, the impact of screw dislocations on the performance of GaN based metal- –semiconductor-metal ultraviolet photodetector is investigated. The experiments reveal that reducing screw dislocations had a strong impact on dark current (~3x decrement) of the devices as well as on the photo- generated current (~20x enhancement) upon illumination (ultraviolet, 325 nm). The responsivity of the pho- todetection device has been increased from 85.05 mA/W to 130.17 mA/W with decreasing dislocation density. Because, higher dislocations created leakage paths that develop trap states which enhances the possibility of recombination process of photo-generated electron-hole pairs leading to lower charge collection. Further, the external quantum effciency increases from 32.51% to 49.76% by reducing dislocation density. The work in this study proposes that reduction of defects/dislocations will be an effective approach to enrich the III-nitride semiconductor system for advancement in optoelectronic devices. 1. Introduction The next generation advanced technology demands highly effcient devices to detect ultraviolet (UV) radiation due to their wide range of potential applications such as solar UV monitoring, ultra secure inter- satellite space communication, missile detection and utilizing UV en- ergy from space for converting optical energy into electrical energy to power various devices [1–6]. These devices are known as photodetectors (PDs) and their performance can be evaluated by many important pa- rameters such as photocurrent, responsivity, response speed, photode- tector gain, detectivity, and noise equivalent power (NEP) [7]. Developing novel structures and experimenting unique methodologies for enhancing the current conduction and thereby, the performance of devices has emerged out to be a special point of interest [8,9]. At pre- sent, the commercialized devices are based on Si and SiC materials which have indirect bandgap. And, in case of an indirect-bandgap semiconductor, an electron transition from the top of the valence band to bottom of the conduction band demands a change not only in the electron energy but also in the electron momentum. Such that, the photon absorption process will also require the involvement of phonons to effectively generate electron-hole pairs which reduces the possibility of effective absorption and utilization of energies closer to the bandgap energy. The numerous advantages of III-Nitride material system having wide-direct bandgap may lead to achieve better values for the vital parameters of an effcient UV detection device, such as cut-off wave- length tunability, high thermal stability and high breakdown feld compared to the existing Si-based photodetector technology [10–12]. Gallium Nitride, GaN is one such member of the nitride family that convincingly has superior material ability to abide harsh working en- vironments because of its inherent visible blindness and good radiation hardness [13]. In comparison to well-established UV enhanced Si tech- nology, the intrinsically visible-blind ability of GaN-based UV PDs eliminates the requirement of costly high-pass optical flters and phos- phors to block low energy photons resulting in cost-reduced and lighter device instrumentation [14]. Furthermore, the high temperature oper- ation of Si-based devices can increase the dark current thereby, reduces its effciency [15]. These undesirable effects from expensive flters as well as low thermal stability are phased out by utilizing GaN material which yields better device performance. [16–18] At present scenario, a wide variety of GaN-based photodetection device structures have been evolved, such as Schottky barrier diodes, p-n junction diode, p-i-n diode and metal–semiconductor-metal (MSM) photodiodes [19–23]. Among * Corresponding author at: CSIR – National Physical Laboratory (CSIR-NPL), Dr K. S. Krishnan Road, New Delhi 110012, India. E-mail address: govind@nplindia.org (G. Gupta). Contents lists available at ScienceDirect Materials Science & Engineering B journal homepage: www.elsevier.com/locate/mseb https://doi.org/10.1016/j.mseb.2020.114879 Received 9 September 2019; Received in revised form 7 August 2020; Accepted 10 October 2020