The influence of water and ethanol adsorption on the optical blinking in InGaN quantum wells

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 ultraviolet 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.