Step multiple quantum well enabled performance enhancement in InGaN/GaN based light-emitting diodes
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TECHNICAL PAPER
Step multiple quantum well enabled performance enhancement in InGaN/GaN based light-emitting diodes Himanshu Karan1 • Mainak Saha2 • Abhijit Biswas1
Received: 11 August 2017 / Accepted: 26 September 2017 Ó Springer-Verlag GmbH Germany 2017
Abstract In this work, we propose and investigate numerically InGaN/GaN based multiple quantum well (QW) blue light-emitting diodes (LEDs) with step quantum well (InGaN)/barrier (GaN) structures. We design four LED structures—(LED-A) InGaN/GaN rectangular quantum well, (LED-B) one down step in the middle of the QW created using sharp increase in In contents, (LED-C) one down step in the middle of the QW and the other down step in the right barrier away from QW and (LED-D) similar to LED-C barring one down step in the left barrier facing the QW. Using well-calibrated APSYS simulation program we compare the variation of output power and internal quantum efficiency of LEDs with input injection current and analyze them in the light of energy band diagram, electric field distribution, carrier concentration and radiative recombination rate. The proposed LED-D exhibits significant improvement in optical output power * 180.7% compared to conventional LED-A. Furthermore unlike other three LED structures, LED-D shows a very low internal quantum efficiency droop of 5.1% only at injection current of 120 mA.
& Himanshu Karan [email protected] 1
Institute of Radio Physics and Electronics, University of Calcutta, 92, Acharya Prafulla Chandra Road, Kolkata 700009, India
2
Institute of Engineering and Management, Maulana Abul Kalam Azad University of Technology, Sector-V Salt Lake Electronic Complex, Kolkata 700091, India
1 Introduction During the past two decades InGaN/GaN based blue light emitting diodes have found widespread commercial applications such as full color display, automotive headlights, mobile platforms and white solid-state lamps (Tsao et al. 2014; Jeong et al. 2014; Yoo et al. 2016; Tansu et al. 2010). Additionally, high-brightness GaN-based LEDs are indispensable for optical interconnects in computers, biological agent detection, disinfection, purification of the environment and many more (Yeh et al. 2015; Wuu et al. 2005; Shakya et al. 2005; Krames et al. 2007). While demands for efficient blue LEDs are high, the performance of blue LEDs are seriously weakened by the critical problem of efficiency droop which refers to the reduction in internal quantum efficiency at high current densities (Verzellesi et al. 2013; Kim et al. 2007). Although the actual mechanism of efficiency droop in InGaN/GaN LEDs still remains debatable, earlier findings suggest some possible reasons responsible for efficiency droop which include Auger recombination (Iveland et al. 2013), electron leakage from active region (Lu et al. 2012), poor hole injection in the device (Ju et al. 2013), polarization effect (Vaxenburg et al. 2013; Schubert et al. 2008), and an inhomogeneous carrier distribution in active region (Wang et al. 2011; Karan et al. 2017). Among them inefficient
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