A vertical-type a-Si:H back-to-back Schottky diode for high-speed colour image sensor

A glass/ITO/a-Si:H/Cr photodiode with a voltage selectable spectral response was fabricated. The diode consists of two back-to-back Schottky junctions. As the bias at the Cr side changes from 1.5 to -1.5 V, three color peak responses can be found, i.e., 480 nm (blue) at V=0.5 V, 530 nm (green) at 1.5 V, and 620 nm (red) at -1.5 V. The basic idea consists of using the different bias voltages to change the location and depth of the photon collection region in which photons with different wavelengths are mainly collected. The photoresponse time was measured under a red LED light injection with an intensity of 150 mu W. The typical photoresponse time for red is 60 ns under -1.5-V bias. These basic studies show that the vertical-type Cr/a-Si:H/ITO back-to-back Schottky diode is a good candidate for a high-speed colour image sensor.<
>