n+-SnO2/a-SiC:H/metal thin-film photodiodes with voltage-controlled spectral sensitivity

n⁺-SnO₂/a-SiC/metal photodiodes with voltage-controlled photosensitivity have been realized by using both carbon-rich and silicon-rich a-SiC alloys. Carbon-rich devices show a response peak located at 530 nm independent of the applied voltage, which in turn only affects the peak height. At variance, in silicon-rich structures the response peak is located at 480, 510, and 570 nm when the applied voltage is -4, 0, and +4 V, respectively, with corresponding quantum yield values of 17, 3, and 25%. For explaining the observed behavior we present a simple model of n⁺-SnO₂/a-SiC/metal diodes, which takes into account light-induced modulation of n⁺-SnO₂/a-SiC barrier height, primary photocurrent generation and photoconductivity effects