The Use of Hydrogen for Defect Reduction in Large Format Infrared Detector Materials

Active defects negatively impact the performance of IRFPAs by increasing noise at various levels up to, and including, catastrophic degradation. Evidence indicates that"killer defects"are related to the interaction of open core screw dislocations with impurities that remain after substrate preparation, prior to HgCdTe growth. This impurity diffusion creates a conducting channel that shorts the junction. The effectiveness of atomic hydrogen for low-temperature cleaning, overlayer removal and stoichiometry recovery for etched semiconductor surfaces has been demonstrated. We will extend this to CdZnTe and Ge substrates and demonstrate cleaning of HgCdTe after process etch steps. Additionally ARI has demonstrated a method for introducing hydrogen into the FPA epilayer during processing. The hydrogen migrates into the HgCdTe and attaches to dislocations and yield-limiting defects, effectively passivating the defect with improvement in both operability and yield. We will use ARI"s process to develop a practical method introducing hydrogen cleaning into HgCdTe processing to produce clean, stoichiometric surfaces prior to growth and passivation while providing hydrogen passivation to mitigate the effect of remaining defects. This will achieve the overall objective of significantly improving operability by reducing defects and dislocations in large format infrared detector materials while also hydrogenating to improve operability.