Investigation of sidewall damage induced by reactive ion etching on AlGaInP MESA for micro-LED application

Abstract

Previous reports have studied the impact of sidewall defects on AlGaInP micro light emitting diode (µLED) only by Current-Voltage-Luminescence (I-V-L) measurements. In this work, we propose an alternative approach to investigate these defects directly after MESA formation, by coupling optical characterization techniques together with Time-of-flight secondary ion mass spectrometry (TOF-SIMS) on AlGaInP square shaped pixels of different sizes formed by BCl3-based Reactive Ion Etching (RIE). It is found that for a 6×6 µm² pixel, the light emission homogeneity is largely impacted by the sidewall defects. From emission efficiency map deduced by temperature-dependent cathodoluminescence measurements, we estimate that 86% of the 6×6 µm² pixel exhibit a lower efficiency than the center. The carriers lifetime extracted from time-resolved photoluminescence (TRPL) measurements on larger pixel begins to decrease gradually at 3 µm from the sidewall due to non-radiative recombinations. On the other hand, the TOF-SIMS analysis shows that residues of boron and chlorine remain on the surface and sidewalls of the pixel after BCl3 etching. These results show the importance to characterize the µLEDs at the MESA step and the necessity to optimize the etching process and the passivation.

Advanced Atomic Layer Deposition Technologies for Micro-LEDs and VCSELs

“…Figure 2 shows a schematic of the micro-LED (μ-LED). As the size of the μ-LED decreases, the sidewall defects have a greater impact on the wafer, leading to a decrease in the luminous efficiency of the chip [ 56 – 58 ]. Passivation in micro-sized LEDs is usually accomplished using plasma-enhanced chemical vapor deposition (PECVD), which uses hydrogen-based precursors to achieve rapid deposition rates [ 30 , 32 ].…”

Surface Recombinations in III-Nitride Micro-LEDs Probed by Photon-Correlation Cathodoluminescence

“…9 However, if these techniques are well suited to characterize the variation in external quantum efficiency (EQE), they do not allow to disentangle changes in internal quantum efficiency (IQE), light extraction efficiency (LEE), or injection efficiency (IE). Thus, to directly estimate the influence of size reduction on Shockley−Read−Hall recombinations and to only be sensitive to IQE variation, time-resolved photoluminescence (TR-PL) spectroscopy 1,10 has been employed. The spatial resolution of such a technique, however, does not allow to directly quantify the surface recombination velocity.…”

Technology and Applications of Micro-LEDs: Their Characteristics, Fabrication, Advancement, and Challenges

“…Boussadi et al investigated the sidewall damage occurring due to RIE on AlGaInP-based red μLEDs. 204 Various methods have been used for defect analysis of μLEDs. Behrman et al utilized nondestructive photoluminescent and cathode imaging for defect analysis.…”

“…Surface defects, which induce substantial carrier leakage current along device sidewalls, is one of the major challenges for high-efficiency GaN/InGaN μLEDs. ,− Surface defects serve as nonradiative recombination hotspots, which severely lower the performance of the devices. Boussadi et al investigated the sidewall damage occurring due to RIE on AlGaInP-based red μLEDs . Various methods have been used for defect analysis of μLEDs.…”