Elimination of Lateral Resistance and Current Crowding in Large-Area LEDs by Composition Grading and Diffusion-Driven Charge Transport

Gallium nitride based light-emitting diodes (LEDs) are presently fundamentally transforming the lighting industry, but limitations in the materials and fabrication methods of LEDs introduce substantial challenges to their future development. Among the remaining key bottlenecks of GaN LEDs are the resistive losses and current crowding that strongly increase the heat generation at high powers. In this work the authors show how a new design paradigm based on diffusion-driven charge transport (DDCT) and selective-area growth (SAG) of GaN can be used to reduce the resistive losses of LEDs below the level achievable with presently available structures. The authors carry out full device simulations and demonstrate SAG of both n- and p-doped GaN on device templates with InGaN quantum wells that can be excited using DDCT. The results indicate that especially when combined with material composition grading, the new approach offers the possibility to substantially reduce the resistive heating in high-power LEDs.