Research on quantum efficiency of exponential-doping GaN monolayer reflection-mode photocathode with ultra-thin emission
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ORIGINAL ARTICLE
Research on quantum efficiency of exponential‑doping GaN monolayer reflection‑mode photocathode with ultra‑thin emission layer Jian Tian1 · Lei Liu1 · Feifei Lu1 Received: 12 November 2019 / Accepted: 25 November 2019 © King Abdulaziz City for Science and Technology 2019
Abstract In this paper, we present an exponential-doping GaN monolayer reflection-mode photocathode whose emission layer is composed of few GaN monolayers with different doping concentrations. To understand its optoelectronic emission performance, the quantum efficiency formula of exponential-doping GaN photocathode with ultra-thin monolayers as the emission layer is obtained. Then, we simulate the impact of recombination velocity of AlGaN/GaN ML interface, recombination velocity of GaN ML/GaN ML interface, thickness of emission layer with GaN monolayers, surface escape probability and surface reflectivity on quantum efficiency based on the formula, respectively. The results imply that interface recombination velocity made a significant contribution to quantum efficiency of photocathode. When interface recombination velocity in AlGaN/ GaN ML and GaN ML/GaN ML is appropriate, they will promote electrons’ escape to the cathode surface and achieve higher quantum efficiency finally. Through our simulation results, a helpful reference can be given for design of exponential-doping GaN monolayer photocathode. Keywords Exponential doping · Quantum efficiency · Ultra-thin emission layer · GaN monolayer
Introduction Over the last 10 years, lot of attention has been paid to twodimensional (2D) materials such as graphene (Novoselov et al. 2004; 2005), MoS2 (Radisavljevic et al. 2011), which possess new attractive mechanical, magnetic and optoelectronic properties owing to their unique confinement structure (Zhang 2015). And they are expected to possess excellent potential for application in nano-optoelectronic devices in the future (Fiori et al. 2014; Zhang et al. 2018a). Şahin et al. (2009) reported a new two-dimensional material denoted as graphene-like GaN (g-GaN) with strong stability and a large band gap by conducting a first-principles investigation on III–V binary compounds monolayer in 2009. There Jian Tian and Lei Liu contributed equally to this work. * Lei Liu [email protected] 1
Department of Optoelectronic Technology, School of Electronic and Optical Engineering, Nanjing University of Science and Technology, Nanjing 210094, People’s Republic of China
are different characteristics between bulk GaN and GaN monolayer for the reason that ultra-thin thickness and quantum confinement effect cause a larger value of band gap on GaN monolayer. This would result in better excitonic effects and durability of higher voltage for g-GaN-based ultraviolet devices, which is significant for enhancing strength of electron–hole interaction and carrier concentrations (Chen et al. 2018). At present, nanomaterials are applied to develop novel environment-friendly slurries (Zhang et al. 2016a, b, 2018b, 2019), diamond wheels (Zhang et al.
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