Improving the Leakage Characteristics and Efficiency of GaN-based Micro-Light-Emitting Diode with Optimized Passivation

Abstract

We investigated the effect of atomic layer deposition (ALD) Al2O3 (50 nm)/plasma-enhanced chemical vapour deposition (PECVD) SiO2 (250 nm) and PECVD SiO2 (300 nm) passivation layers on the leakage current and efficiency of InGaN-based micro-LEDs with different sizes. Regardless of passivation layers, the leakage current increased with decreasing LED size and increasing reverse bias. Emission microscopy examination showed that with increasing reverse bias, the number of defect-related emission spots and their intensities increased. For the micro-LEDs <50 μm, the emission spots were mainly located at the sidewall regions. Above −10 V, the single PECVD SiO2 passivation layer gave higher leakage current than the double ALD-Al2O3/PECVD-SiO2 layer. The micro-LEDs with the single passivation layer gave the ideality factors of about 2.0, while that with the double layer exhibited values smaller than 2.0. The micro-LEDs with the double passivation layer exhibited external quantum efficiency peaks at lower current density compared to those with the single layer. It was shown that smaller micro-LEDs were more sensitively dependent on the types of the passivation layers. These results exhibit that the ALD-Al2O3/PECVD-SiO2 passivation layer is more effective in suppressing the sidewall damage-induced current than the PECVD-SiO2 layer.

Impact of sidewall conditions on internal quantum efficiency and light extraction efficiency of micro-LEDs

“…Similar result of suppressing YL band by sol-gel SiO2 was reported elsewhere [16]. The most important thing in the performance of µLEDs is the sidewall condition [34][35][36][37][38][39][40]. Except for special cases, such as semipolar and nonpolar GaN LEDs, most GaN-based LED wafers are grown on c-plane sapphire, and hence the sidewall should have a non-polar surface such as m-plane orientation (Figure 2).…”

Impact of Sidewall Conditions on Internal Quantum Efficiency and Light Extraction Efficiency of Micro‐LEDs

“…Similar result of suppressing YL band by sol-gel SiO2 was reported elsewhere [16]. The most important thing in the performance of µLEDs is the sidewall condition [34][35][36][37][38][39][40]. Except for special cases, such as semipolar and nonpolar GaN LEDs, most GaN-based LED wafers are grown on c-plane sapphire, and hence the sidewall should have a non-polar surface such as m-plane orientation (Figure 2).…”

Dennard Scaling in Optoelectronics: Scientific Challenges and Countermeasures of Micro‐LEDs for Displays

“…[39] However, it should be acknowledged that the potential of typical QW LEDs for further improvement is limited, which can be seen from Figure 3e where results on QW LEDs reported in the technical literature are summarized. [40][41][42][43][44][45][46][47][48][49][50][51] Even for largesize SSL LEDs fabricated under state-of-the-art techniques where size-dependent effect can be neglected, the J PEAK (several A cm −2 ) is still far higher than the expected working current density for Micro-LEDs. This is partially because carriers tend to form Wannier excitons (rather than Frenkel excitons in GaN-based materials), where the carrier interaction is much looser than that in OLEDs so that a large n cannot be achieved naturally.…”