Carrier loss analysis for ultraviolet light-emitting diodes

This study investigates the physical mechanisms behind carrier loss in a top-emitting LED with U-shaped n-contact and semi-transparent p-contact using the three-dimensional (3D) device simulation software APSYS which was improved for the purpose of this investigation. The software self-consistently combines carrier transport, quantum well effects, self heating, and optical ray tracing. The model includes drift and diffusion of electrons and holes, Fermi statistics, built-in polarization and thermionic emission at hetero-interfaces, as well as spontaneous and defect related Shockley-Read-Hall (SRH) recombination of carriers. For the quantum wells, Schrodinger and Poisson equations are solved iteratively to account for bias-dependent changes. A recent compilation of wurtzite band structure parameters is used in the simulation.