This paper will survey and review the evolution and state-of-the-art of extrinsic silicon IR focal plane array technology. Extrinsic silicon photodetectors are capable of optimum infrared detection ranging from below 2 to well above 20 micrometers. Arrays of silicon detectors have been used in focal planes for both ground- and space-based operational systems such as the highly successful Infrared Arrowing Satellite (IRAS). The special properties of these detectors when they are used in conjunction with state-of-the-art charge-coupled device (CCD) multiplexing devices will have a significant impact on all future focal plane developments. The status and futured development potential of these infrared charge-coupled devices (IRCCD's) will be discussed in this paper. The concepts for and progress made toward realizing two-dimensional mosaic focal planes integrating silicon CCD multiplexers and extrinsic silicon detector array will be reviewed. Finally, the potential and applications of silicon focal planes will be assessed.