ToF-SIMS and XPS coupled characterization of HgCdTe surface oxides for infrared detection applications

Because of their unique material properties, HgCdTe-based photodiodes are among the leading candidates for background-limited performance infrared detectors at room temperature. Nonetheless, surface oxide formation, induced by manufacturing processes and environmental exposure, critically affects their electrical characteristics. Consequently, precise control of the alloy surface chemistry is essential. In this work, time-of-flight secondary ion mass spectrometry (ToF-SIMS) was used to complement x-ray photoelectron spectroscopy (XPS) to characterize oxides generated through native and plasma oxidation of HgCdTe. XPS analysis demonstrated that tellurium oxide is the dominant oxide component, with evidence suggesting contributions from mercury and cadmium oxides. ToF-SIMS employing low-energy MCs+ depth profiling provided elemental distribution profiles within the oxide layers and identified impurities introduced during oxide formation. The combined XPS and ToF-SIMS analysis provided new insights into the HgCdTe plasma oxide structure, demonstrating its effectiveness in identifying subtle surface chemistry changes. Furthermore, effective minority carrier lifetime measurements, employing photoluminescence decay, were conducted to determine the influence of chemical changes on material electronic properties. Given its sensitivity to impurities, this parameter serves as a key metric for process evaluation and optimization, reflecting contributions from both bulk and surface properties. Through these measurements, the impact of surface oxide introduction on effective minority carrier lifetime was determined, demonstrating a link between physicochemical attributes and performance degradation.