Here, we demonstrate the improvement of the InGaN green micro-LED’s efficiency by application of the hydrogen passivation method. We utilize the phenomenon of Mg dopant deactivation by hydrogen in p-doped GaN, which leads to up to 10-fold increase in its resistivity^[1]. In this experiment, we have applied the hydrogen passivation to the micro-LED pixel’s sidewalls, after they were exposed by the mesa etching process. The local increase in p-GaN’s resistivity led to the suppressed current injection in the sidewall region. It is illustrated in Figure 1 by the formation of the dimmed frame along the pixel’s perimeter, recorded by the optical microscope imaging of LED’s electroluminescence under forward bias^[2].
Suppression of the current injection in the sidewall region was performed to reduce the probability of the non-radiative recombination, which increases with the presence of the surface defects, introduced by the mesa etching process. We have compared micro-LEDs with and without hydrogen passivation in the case of square pixels of two sizes – 20x20 µm² and 100x100 µm². In both cases, hydrogen passivation led to enhanced device efficiency, 2.6 times and 1.8 times increase in peak on-wafer wall-plug efficiency in the case of 20x20 µm² and 100x100 µm², respectively, as demonstrated in Figure 2^[2].