10 GaN - based Light - Emitting Diodes

Light-emitting diodes (LEDs) offer several advantages over traditional light sources, such as smaller size, longer lifetime, higher efficiency, and greater mechanical ruggedness. Continuing developments in LED technology are producing devices with increased output power and efficiency as well as a wider range of colors [1]. Recent progress in the fabrication of GaN-based compound semiconductors enabled the practical breakthrough of short-wavelength LEDs that emit green, blue, or ultraviolet light [2]. In particular, compact ultraviolet (UV) light sources are currently of high interest for applications in whitelight generation, short-range communication, water purification, and biochemical detection. Prime candidates are nitride LEDs with AlGaN quantum wells. However, their performance is still below the requirement for practical applications. We present here a self-consistent physics-based three-dimensional (3D) simulation of an AlGaN/GaN LED and study performance limiting internal mechanisms. Good agreement with measured device characteristics [3] is achieved by refinement of the physical model and by calibration of material parameters. Based on this agreement, we are able to analyze the practical impact of microscale and nanoscale physical effects such as current crowding, carrier leakage, nonradiative recombination, and built-in polarization. The device structure is given in the next section. Section 10.3 describes the theoretical models and the material parameters used. The main simulation results are presented and discussed in Sect. 10.4.