Color image sensor

Abstract

The present invention relates generally to a photodetector, and more particularly to a photodetector formed by a static induction transistor. The present invention includes the following constituent elements: In the photodetector formed by a static induction transistor, an n.sup.+ -type buried layer is provided, as a drain or source region of the photodetector, for limiting the thickness of a high resistivity i-type layer between a p.sup.+ -type region forming a gate and a substrate. Letting the wavelength of light incident to the surface of the photodetector and an absorption coefficient for the incident light be represented by .lambda..sub.i and .alpha..sub.i (.lambda..sub.i), respectively, the distance between the in junction of the abrupt pin junction and the surface of the photodetector x.sub.i is ##EQU1## the ratio between the area A(.lambda..sub.i) of each gate portion for selectively detecting light of the specified wavelength .lambda..sub.i and the total area A.sub.tot of the gate is selected as follows: where e=2.718, .eta.(.lambda..sub.i) is required quantum efficiency for the wavelength .lambda..sub.i and R(.lambda..sub.i) 15 a refractive index for the wavelength .lambda..sub.i, and the thickness Wi of a depletion layer and the maximum depth x.sub.i.sbsb.max of the depletion layer for detecting the specified wavelength .lambda..sub.i are selected as follows: ##EQU2## thereby providing selective spectral responsivity for the specified wavelength .lambda..sub.i. Letting three specified wavelengths of blue, green and red light be represented by .lambda..sub.1, .lambda..sub.2 and .lambda..sub.3, the total area of the gate is A.sub.tot =A(.lambda..sub.1)+A(.lambda..sub.2)+A(.lambda..sub.3). Pixels for detecting the three wavelengths are arranged in a honeycomb-like pattern, as shown in FIG. 8. For obtaining the maximum photodetection sensitivity for the three wavelengths, for example, 460, 550 and 660 nm, the diffusion depth x.sub.jp + of the gate portions and the depletion layer width Wi between the gate and the n.sup.+ -type buried source region are selected as given below in Table 1: TABLE 1 ______________________________________ x.sub.i.sbsb.max Wi x.sub.jp.spsb.+.sbsb.max -x.sub.jn.spsb.+ .lambda. ______________________________________ B 0.63 .mu.m 0.4 0.2 3.0 460 nm G 1.53 .mu.m 0.9 0.5 2.2 550 R 3.57 .mu.m 2.3 1.3 0 660 ______________________________________

Dependencies are inferred from the claim text.