The impacts of sidewall passivation via atomic layer deposition on GaN-based flip-chip blue mini-LEDs

In order to investigate the photoelectric characteristics of 80 × 120 μm2 mini-light-emitting-diodes (mini-LEDs) with sidewall passivation by atomic layer deposition (ALD), this paper uses the techniques of spectrometer-based spectroradiometer and microscopic hyperspectral imaging (μ-HSI). The temperature-dependent electroluminescence is measured using a spectrometer-based spectroradiometer. By analyzing the rising parts of external quantum efficiency at room temperature with a two-level model, the difference of physical mechanisms between mini-LEDs with ALD and without ALD are determined. In addition, the thermal quenching indicates that the ALD sidewall passivation can enhance the temperature stability of the mini-LEDs. The ALD sidewall passivation also enhances the light extraction efficiency according to the theoretical calculation of transmittance. Moreover, the μ-HSI technique is used to evaluate different local areas of mini-LEDs. The obtained results reveal the optimization on lateral distribution of current density within the chip after sidewall passivation.