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(Color online) (a) Conventional CMOS image sensor. Case of light normally incident upon the sensor is shown for middle pixel: microlens (focal length f1) focuses light onto center of photodetector. Largest angle (φ1) at which light can be incident and still be focused onto photodetector (diameter D) is shown for right pixel. (b) CMOS image sensor with lightpipes. Each microlens (focal length f2) focuses light onto lightpipe entrance, rather than onto the photodetector. Largest angle (φ2) at which light can be incident and still be focused onto lightpipe entrance and detected by photodetector is depicted for right pixel.
(Color online) (a) SEM image of SiNx high aspect ratio lightpipes with diameters of 0.9 and 5 μm, and heights of 7.4 μm. Image obtained prior to removal of Al disk etch mask. (b) Schematic of complete device structure; only functional parts are shown. (c) Optical microscope image of light pipe-free device fabricated for comparison purposes. (d) Optical microscope image of completed light pipe device.
(Color online) Scanning photocurrent microscopy maps of (a) light pipe and (b) light pipe-free devices. (c) Photocurrent vs x-distance for lightpipe (“WP EXP”) and lightpipe-free (“WOP EXP”) devices measured along paths indicated in panels (a) and (b) with black lines. (d) Photocurrent vs vertical sample position (z), for another pair of lightpipe and lightpipe-free devices, measured under higher laser power.
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