3D Simulations on Realistic GaN-Based Light-Emitting Diodes
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3-D simulations on realistic GaN-based light-emitting diodes Simon Li, Z.Q. Li, O. Shmatov, C. S. Xia1 and W. Lu1 Crosslight Software Inc 206-3993 Henning Drive Burnaby BC V6C 6P7 Canada 1 National Lab for Infrared Physics, Shanghai Institute of Technical Physics Chinese Academy of Sciences 500 Yu Tian Road, Shanghai 200083, China ABSTRACT Comprehensive multiscale models have been employed to simulate the realistic GaN based light-emitting diodes (LED) using 3D finite-element analysis. The advanced features include drift-diffusion model for carrier transport, self-consistent Poisson-Shrodinger and K·P models for multi-quantum well band structure, quantum tunneling model for heterojunction, spontaneous and piezoelectric polarization models for built-in electric field, heat flow model for self-heating and ray-tracing model for photon extraction. All the advanced capabilities have been integrated into our software APSYS[1]. In this paper, we present the 3D simulations on the InGaN/InGaN LEDs. Based on the detailed simulation results, we were able to analyze the impact of micro- and nano-scale physical effects such as current crowding, carrier leakage, built-in interface charge and self-heating on the internal efficiency of the device. The macro-scale effect of the geometry on photon extraction was analyzed using 3D ray-tracing technique. Results of different structures will be given to demonstrate the power of the software in handling complicated realistic LED geometries. The simulation results can be used to optimize the design of quantum well layers, blocking layer materials and electrode geometries etc. INTRODUCTION Extensive experimental effort has been devoted to achieve high-efficiency III-nitride lightemitting diodes (LEDs) by improving the quality of III-nitride materials, optimizing multiquantum-well (MQW) device structure and efficient light-extraction packaging [2-3]. Compared with a growing number of expensive and time-consuming experimental studies, in-depth simulations on the performance of LEDs are rarely reported. Although basic theoretical models are available for LED simulation, it still lacks detailed understanding of microscopic process, which restricted the design and optimization of LED device structure. For GaN based LEDs, computer simulations are very useful for device design issues such as current leakage, light extraction, current crowding and thermal effects. Kim et al. [4] have reported a 2D simulation analysis of InGaN/GaN LED, but the 3D effects on the current spreading and light extraction were not addressed. Piprek et al. [5] have done the simulation and analysis of AlGaN/GaN UVLEDs using APSYS software. In this paper, we use our advanced APSYS software to simulate comprehensively the real 3D GaN LEDs with different structures. Most important physical models are included for the simulations, which provide complete description of the LED operations. The presence of InNcomposition modulation within the InGaN quantum wells has been taken into account to explain the EL spectr
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