We studied the adsorption of liquids over the surface of InGaN quantum well based wide band-gap devices and found that the immersion in certain liquids has noticeable effects on the optical blinking phenomena. We used two samples with different indium concentrations, emitting on the green and blue range, and immersed them while under direct illumination with 365~nm UV light. We found that especially water and ethanol provoked evident optical variations compared to observation in air. While blinking spots can be observed irrespective of the In concentration, their contrast and luminosity increased for samples with the emission in the 510~nm range, rather than for those in the 460~nm. Based on these results, we put forward the hypothesis that the presence of liquids induces the formation of radiative centers, possibly complexes related to intrinsic defects binding with adsorbed impurities, such hydrogen or oxygen.
The blinking phenomenon in InGaN single quantum wells is a phenomenon where localized photoluminescence changes over time. Understanding its physics is important for the manufacture of more efficient light emission diodes. We present a study using two InGaN single quantum well samples, emitting at 460 and 510 nm wavelength, respectively. We confirmed that the luminescence intensity fluctuates in localized blinking regions, and we found that these optical variations are not random but are instead correlated in pairs, with either positive or negative coefficient, to a distant reference blinking point. Measurements were performed to obtain standard deviation and cross-correlation maps. Invoking the quantum confined Stark effect, we realized a simple phenomenological model that shows how charge carriers are exchanged among pairs of adjacent opposite correlation regions. As a result, it is suggested that the phenomenon is caused by fluctuations in the number of these exchanged carriers. Our model gives an explanation for the blinking phenomenon in InGaN single quantum wells, and it is important for a deeper understanding to InGaN-based materials.
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