An ultraviolet radiation sensor using differential spectral response of silicon photodiodes

An ultraviolet (UV) sensor is demonstrated with high sensitivity in the UV waveband and low sensitivity in the visible (VIS) and near-infrared (NIR) wavebands, utilizing only bulk silicon technology. The developed sensor utilizes the differential spectral response of photodiodes (PDs) with a high UV sensitivity (PD1) and a low UV sensitivity (PD2), for UV signal extraction under a VIS and NIR light background. To suppress the effects of incident light spatial strength distribution over the sensor, PD1 and PD2 were arranged in a checkered pattern of 8×6 PDs. High Signal to Noise Ratio (SNR) for UV signal extraction was achieved by a developed prototype UV sensor circuit consisted of charge amplifiers connected to PDs and a differential amplifier. The fabricated PD chip has a total area of 1.2 mm2, PD1 and PD2 showed a sensitivity of 0.16 A/W and 0.02 A/W at 310 nm, respectively. The spectral response of the UV sensor was measured and the UV waveband selective sensitivity was successfully obtained.