Patent ID: 7352454
Filing Date: 2008-04-01
Classification: G01J,G01S,H01L

Abstract:
1. A CMOS-implementable semiconductor photodetector useable in a system that illuminates a target with optical energy having a modulated periodic waveform that includes a high frequency component, generated in response to signal provided by a clock generator, and that detects a fraction of said optical energy reflected by said target with at least one said semiconductor photodetector, said photodetector comprising: a semiconductor substrate having a surface upon which said incoming optical energy can impinge onto an optical energy sensitive region, said surface defining an x-direction and a y-direction; at least a first elongate-shaped polysilicon gate disposed on said surface parallel to said y-direction, said first gate coupleable to a first bias clock signal, synchronously generated by said clock generator, that is high during a first bias regime to detect and collect charge generated by at least a fraction of said incoming optical energy; a first source region formed in said substrate adjacent a distal end of said first gate; at least a second elongate-shaped polysilicon gate disposed on said surface parallel to said first elongate-shaped gate and spaced-apart in said x-direction a distance substantially shorter than a length of either said gate, said second gate coupleable to a second bias clock signal synchronously generated by said clock generator; a second source region formed in said substrate adjacent a distal end of said second gate; wherein responsive to said first bias clock signal and said second bias clock signal, photoelectic charge generated in said substrate is moved in said x direction to become trapped beneath an elongate-shaped gate and is then moved in said y-direction to an adjacent source region for collection, charge movement in said y-direction being slower than charge movement in said x-direction, wherein modulation contrast of said photodetector is enhanced.