Efficiency cliff in scaling InGaN light-emitting diodes down to submicron

The top-down submicron fabrication of blue-emitting light-emitting diodes on Qromis Substrate Technology substrates is reported. Light-emitting diodes with mesa sizes as small as 250 × 250 nm2 show ideal forward voltage and low leakage current density. It is observed that sidewall treatment and passivation methods used in micro-light-emitting diodes (2–20 μm) do not lead to the same level of sidewall recombination suppression for submicron ones (<1 μm), as evidenced by a ∼70% decrease in peak external quantum efficiencies when mesa sizes are scaled from 2 μm down to 250 nm. This is attributed to the lateral carrier diffusion being comparable to the mesa size, regardless of the sidewall passivation and recovery. The results call for rethinking the impact of sidewalls in emerging top-down fabricated (sub)micrometer-light-emitting diodes.