electronics Article Numerical Model of Current Flow and Thermal Phenomena in Lateral GaN/InGaN LEDs Zbigniew Lisik, Ewa Raj * and Jacek Podgórski   Citation: Lisik, Z.; Raj, E.; Podgórski, J. Numerical Model of Current Flow and Thermal Phenomena in Lateral GaN/InGaN LEDs. Electronics 2021, 10, 3127. https://doi.org/10.3390/ electronics10243127 Academic Editors: Ilgu Yun, Soon Il Jung, Chang Eun Kim and Edward Namkyu Cho Received: 24 November 2021 Accepted: 13 December 2021 Published: 16 December 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). Department of Semiconductor and Optoelectronic Devices, Lodz University of Technology, Politechniki 10, 93-590 Lodz, Poland; zbigniew.lisik@p.lodz.pl (Z.L.); jacek.podgorski@p.lodz.pl (J.P.) * Correspondence: ewa.raj@p.lodz.pl Abstract: GaN-based light-emitting diodes (LEDs) became one of the most widely used light sources. One of their key factors is power conversion efficiency; hence, a lot of effort is placed on research to improve this parameter, either experimentally or numerically. Standard approaches involve device- oriented or system-oriented methods. Combining them is possible only with the aid of compact, lumped parameter models. In the paper, we present a new electro-thermal model that covers all the complex opto-electro-thermal phenomena occurring within the operating LED. It is a simple and low computational cost solution that can be integrated with package- or system-oriented numerical analysis. It allows a parametric analysis of the diode structure and properties under steady-state operating conditions. Its usefulness has been proved by conducting simulations of a sample lateral GaN/InGaN LED with the aid of ANSYS software. The results presented illustrate the current density and temperature fields. They allow the identification of ‘hot spots’ resulting from the current crowding effect and can be used to optimise the structure. Keywords: LED; electro-thermal model; GaN; energy transfer mechanisms; ANSYS 1. Introduction GaN-based light-emitting diodes (LEDs) are recognised as attractive solid-state light- ing (SSL) sources due to their advantages compared to traditional light sources, such as lower electric power consumption, higher reliability, very long lifespan, and high colour rendering index. It causes intensive investigation of their design, technology, and features, carried out by both by industry and university research teams. The studies focus on dif- ferent design concepts such as vertical [1–3], lateral [4,5] or 3D core-shell [6–9] devices, discussing their fabrication technologies [10–12], or aiming at their features employing experimental [13,14] or numerical [15–17] approaches. SSL LEDs belong to electronic power devices, which means that the conversion efficiency of the delivered electric power into the output optical power is the basic factor for their design. Furthermore, they typically operate with maximum currents. It implies additional constrains of their design, besides those resulting from the one-dimensional physical phenomena taking place in any diodes, e.g., for signal processing applications. The inherent attribute consists in the presence of the lateral component of the current flow, which results from the fact that both the anode contact and the optical window for the light emission are located on the same surface of the diode structure. In general, the radiative recombination below an optical window gives the contribution to the emitted signal. The ohmic contact of the anode above the active region may prevent light escape; therefore, the size, shape, and properties of the contact are of crucial importance for the final efficiency of the diode [18,19]. The two-dimensional current distribution, and more precisely its nonuniformity, is another parameter that must be considered in the case of the power LEDs. It can lead to the disruption of current uniformity in quantum wells, which can result in a decrease in device performance, as well as to the generation of ‘hot spots’ due to the current crowding effect. The increase in local current density is accompanied by Electronics 2021, 10, 3127. https://doi.org/10.3390/electronics10243127 https://www.mdpi.com/journal/electronics