Characteristics and simulation analysis of GaN-based vertical light emitting diodes via wafer-level additional surface roughening process

We report the device characteristics of InGaN/GaN blue vertical light emitting diodes (VLEDs) by additional KOH surface roughening process through the wafer‐level fabrication/test, and their simulation analysis in terms of electrical and optical properties. The influence of additional KOH etching time on the evolution of the rough surface and the device performance of VLEDs was investigated. With applying the additional surface roughening, the average operating voltage was gradually increased. In contrast, the average optical output power was increased upto a certain roughening time, but then it decreased again. As a whole, by applying an adequate additional roughening process, the optical power was improved without noticeable increase in the operation voltage. From the simulated current density and light extraction efficiency results, these device behaviours were well explained by the current crowding and bulk absorption effects.