Visible-blindness in photoconductive and photovoltaic AlGaN ultraviolet detectors

The influence of the photodetection mechanism on the performance of AlGaN ultraviolet (UV) detectors is analyzed by studying the characteristics of photoconductors and photovoltaic Schottky diodes fabricated on the same samples. The photoconductive response below the bandgap is not a direct function of the absorption coefficient. Instead, it is amplified by the dominant photoconductive responsivity mechanism, which is attenuated as the chopping frequency increases. On the contrary, photovoltaic detectors are characterized by a sharp UV/visible contrast, mainly dependent on the absorption properties of the material. Thus, these detectors are more suitable for selective UV applications, such as ozone layer monitoring or flame detection.