Investigation of surface passivation thin film materials for improved predictable quantum efficiency detectors

We report the preliminary results from our study of different surface passivation thin film materials and deposition processes for development of PQEDs with excellent performance and stability at room temperature and cryogenic temperatures. Our work aims at maximizing the fixed charge density in the dielectric and the effective minority charge carrier lifetime as well as reducing the optical absorption of the dielectric in the visible range to a negligible level. We have so far demonstrated a fixed charge density of > 5x10cm and effective lifetime of > 4 ms for ptype FZ wafers passivated with PECVD SiNx or a stack of thermal SiO2 and PECVD SiNx. For ntype FZ wafers passivated with ALD Al2O3, we have obtained an effective lifetime of ~20 ms.