Photoluminescence Monitored Sustainable Digital Photocorrosion of GaAs/Al0.35Ga0.65As Quantum Well Microstructures

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Digital photocorrosion (DIP) of GaAs/AlGaAs nanoheterostructures is an attractive method for detecting surface‐immobilized electrically charged biomolecules such as bacteria. The process is normally carried out in ammonia‐ or phosphate‐buffered saline and monitored in situ to reveal photoluminescence (PL) intensity maximum (PLmax) when the photocorrosion front crosses the GaAs‐AlGaAs interface. The temporal position of PLmax plotted as a function of the concentration of surface‐immobilized biomolecules allows calibration of the process and detection of unknown concentrations of bacteria. Successive employment of numerous GaAs‐AlGaAs interfaces in a stack of GaAs/AlGaAs quantum wells (QWs) for biosensing is drastically restricted due to the diminishing PL intensity related to accumulation of Al oxides and other byproducts on the surface of processed samples. Herein, the application of a cyclic injection of NaOH solution for chemical “sweeping” of the AlGaAs surface to maintain a sustainable DIP process manifested by nonvanishing amplitude of the PL signal is reported. The successful measurement of eleven PLmax with comparable amplitudes from the same GaAs/AlGaAs QW microstructure paves the way to the development of an advanced biochip delivering a large number of data points.