Table 2 State-of-the-art blue micro-LED (1–10 μm) performance based on RIE mesa insulation and sidewall treatment
From: Advanced technologies in InGaN micro-LED fabrication to mitigate the sidewall effect
InGaN blue micro-LEDs | Reference | Wavelength | Pixel size | EQE peak |
447 nm | 10 μm | 40.2% | ||
Operation voltage | Reverse leakage | EQE droop | ||
3.5 V at ~50 A cm−2 | / | 45.7% from JEQE-peak (26 A cm−2) to 900 A cm−2 | ||
ICP-RIE condition or description | ||||
Top-down RIE from the ITO to the n-GaN. | ||||
Techniques to mitigate the sidewall effect | ||||
Omnidirectional reflector (ODR) via ion beam deposition, with alternating layers of SiO2 and tantalum Ta2O5 with a final layer of Al2O3. | ||||
Reference | Wavelength | Pixel size | EQE peak | |
455 to 470 nm | 2 μm | ~13.4% | ||
Operation voltage | Reverse leakage | EQE droop | ||
~2.7 V at 10 A cm−2 | < 600 pA (detection limit) | ~56.6% from JEQE-peak (12 A cm−2) to ~1000 A cm−2 | ||
ICP-RIE condition or description | ||||
CH4/H2/Ar RIE removed ITO, and Cl2/N2 ICP etching removed InGaN/GaN layers. Subsequently, a short SiCl4 RIE treatment was used to improve ohmic contact. | ||||
Techniques to mitigate the sidewall effect | ||||
A room-temperature KOH treatment was conducted for around 30 min to eliminate plasma damage. Then, 20 nm of ALD-Al2O3 (trimethylaluminum, TMA + H2O) was then deposited at 300 °C to passivate the sidewall surface, followed by 250 nm PECVD-Si3N4 at 250 °C for electrical insulation. | ||||
The performance of pixels with other sizes in this work | ||||
For 5 and 10 μm blue micro-LEDs: EQE ~ 10.6% and ~9.4% | ||||
Reference | Wavelength | Pixel size | EQE peak | |
466.6 nm | 1.3 × 1.5 µm2 | 22.3% | ||
Operation voltage | Reverse leakage | EQE droop | ||
~2.6 V at 10 A cm−2 | ~1 × 10−7 A cm−2 at −3 V | / (EQE peak at ~12 A cm−2) | ||
ICP-RIE condition or description | ||||
A low radio frequency power of 30 W has been opted to reduce plasma-induced sidewall damage. | ||||
Techniques to mitigate the sidewall effect | ||||
KOH and H3PO4 etching to reduce surface defects. 5 min N2O plasma treatment with the radio frequency power of 5 W to minimize defect density. 1 µm SiO2 layer as a passivation and planarization layer. | ||||
Other characterizations of interest | ||||
Luminance >1 × 107 nits, light power densities > 4 × 104 mW cm−2 at ~150 A cm−2 | ||||
Reference | Wavelength | Pixel size | EQE peak | |
~465 nm | 1 μm | 13.02% | ||
Operation voltage | Reverse leakage | EQE droop | ||
~2.4 V at 10 A cm−2 | / | ~45.5% from JEQE-peak (20 A cm−2) to 1000 A cm−2 | ||
ICP-RIE condition or description | ||||
ICP-RIE (Cl2/Ar/BCl3191) was used to etch GaN-based materials. | ||||
Techniques to mitigate the sidewall effect | ||||
200 nm-thick PECVD-SiO2 served as a passivation layer. | ||||
The performance of pixels with other sizes in this work | ||||
For 2 and 5 μm blue micro-LEDs: EQE ~ 15.6% and ~19.1% | ||||
