PC-Thu-P14 - Minimising plasma-induced damage on nGaN for uLED mesa etching applications
2. Physics and characterizationPoster
Zhengfei Wei1, Andrew Newton1, Stuart Robertson2
1 Oxford Instruments Plasma Technology, Bristol BS35 4GG, United Kingdom
2 Loughborough Materials Characterisation Centre, Department of Materials, Loughborough University, Loughborough LE11 3TU, United Kingdom
Abstract text
Micro Light Emitting Diodes (μLEDs) are considered the next-generation display technology, particularly for applications in wearable devices such as smartwatches, virtual reality, and augmented reality. To achieve high-resolution and high-brightness displays, smaller μLED dimensions are required. However, as the size of μLEDs decreases, the effect of the mesa sidewalls becomes more significant, leading to size-dependent leakage current density and reduced external quantum efficiency [1]. Mesa etching on GaN plays a critical role in device fabrication by isolating the active regions. Traditional mesa etching is typically performed using the Inductively Coupled Plasma Reactive Ion Etching (ICP-RIE) process, which introduces sidewall damage due to ion bombardment and ultraviolet photon irradiation. To mitigate this damage, post-wet treatments using TMAH and KOH have been reported [2]. In this abstract, we present the impact of ICP-RIE etching with optimised bias power on minimising sidewall damage while improving etch rate.
1.5 μm Si-doped (~1.5×10¹⁸ cm⁻³) GaN, grown on sapphire substrates by metal-organic chemical vapour deposition, was etched using a standard mesa process with μLED masks. The etch rate in the optimised process, 50 nm/min, was competitive to present a realistic throughput for an LED manufacturing step. Photoluminescence (PL) measurements showed a 97.3% decrease in PL intensity for the standard mesa process compared to the unetched sample, whereas the optimised mesa etch process resulted in only a 31.8% decrease. Furthermore, Cathodoluminescence (CL) measurements revealed a 79.6% reduction in intensity for the standard mesa process, while the optimised process showed a much lower reduction of 15.7%. These results suggest that minimising ion bombardment during the mesa etching process can significantly reduce sidewall damage.
Future work will focus on investigating the impact of the low-damage mesa etch process on the performance of fully fabricated μLED devices.
[1] Smith, J. M. et al. Appl. Phys. Lett.116, 071102 (2020).
[2] Park, J. H. et al. Adv. Optical Mater.11, 2203128 (2023).