Effect of the self-aligned etching thin p-GaN layer on the performance of AlGaN-based DUV LEDs with various chip sizes

The light extraction efficiency (LEE) for deep ultraviolet light-emitting diodes (DUV LEDs) is significantly sacrificed by the absorption of p-GaN layer. In this work, the self-aligned etching process is employed to laterally over-etched periphery thin p-GaN under the p-electrode by 10 μm to further improve the performance of AlGaN-based LEDs with various chip sizes. We find that when compared with reference devices with chip sizes of 40 × 40 μm², 60 × 60 μm² and 100 × 100 μm², the optical power levels for the proposed DUV LEDs are enhanced by 16.66 %, 11.41 % and 7 %, respectively. The most optical power enhancement can be obtained for the 40 × 40 μm² DUV micro-LED chip. Hence, it is indicated that the laterally over-etched p-GaN design is more effective in increasing the LEE for DUV LEDs with reduced chip size. This shows the potential of self-aligned etching p-GaN process in enhancing the LEE of DUV micro-LEDs. In addition, the lateral over-etched thin p-GaN suppresses the carrier diffusion to the device edge, which reduces the diffusion capacitance therein, hence leading to an increased -3dB bandwidth to 55.4 MHz from 75.9 MHz for the packaged device of 100 × 100 μm².