Optimization of a-Si:H-based three-terminal three-color detectors

Three-terminal three-color n-SiC:H/a-Si:H-based TCO/PINIP/TCO/PIN/metal detectors are presented. Assemblies having different surface roughness of transparent conducting oxide (TCO) layers are compared with regard to the external steady-state characteristics and transient behavior. The roughness of the sputtered TCO surface can be modified by an etching treatment. With the selection of smooth or textured TCO surfaces, the wave propagation of light within the device is controlled. This design technique can be exploited to optimize the color separation and improve the reproducibility of spectral responsivities in the assemblies. The examined assemblies exhibit very selective spectral responsivity for the fundamental chromatic components (red-green-blue) and a linear photocurrent-generation rate relationship over more than five orders of magnitude of illumination intensity. Since the color detection of blue and green light is performed in the PINIP structure by bias switching, the transient current response of the PINIP structures is investigated. A reciprocal relationship between the delay time and illumination intensity is established. An optimum operation region for the switching voltages is determined with regard to the quality of color separation, dynamic range, and transient behavior.