Electroluminescence uniformity in green LEDs and dual color blue/green stacking LEDs

The uniformity of Electroluminescence (EL) of green and blue/green stacking InGaN Light Emitting Diodes (LED) has been studied and analyzed by various techniques. Comparative measurements of Photo‐Luminescence (PL), Cathode‐Luminescence (CL) and EL allow us to conclude that non‐uniform distribution of EL in studied LEDs is caused by non‐uniformity of acceptors distribution over the p‐GaN area. It was found that there are some defective areas in p‐GaN having locally low level of acceptor concentration. These areas correspond to the surface hexagonal shaped pyramids on p‐GaN surface. The locally low doping level changes the field distribution, injection properties and the EL emission properties for these defective points. Optimization of p‐GaN growth conditions will improve the EL uniformity and increase the efficiency of green and blue/green LEDs. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)