Amorphous silicon photodiodes are increasingly being used as fundamental components in digital diagnostic medical imaging system including large area chest radiography, mammography and real time fluoroscopy. The intrinsic a-Si:H material (i-a-Si:H), commonly deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD), is well known to suffer from both light and bias stress induced instabilities over time that can result in an increase in dark current and a decrease in photoconductivity. In contrast, research in Hot-Wire Chemical Vapor Deposition (HWCVD) indicates that a-Si:H films grown by HWCVD can have superior physical and electronic properties to those grown by PECVD.
In this research, we report on the material properties and stability of i-a-Si:H material by comparing the photoconductivity degradation of the HWCVD and PECVD films over time. Then, we discuss the p-i-n diode fabrication process and examine the leakage and photo-current degradation in the HWCVD and PECVD photodiode structures over time via bias and time stress measurements. Also, we investigate the quantum efficiency degradation over time in a-Si:H p-i-n detectors grown by PECVD.