A miniature infrared (IR) sensor for military surveillance — such as identifying distant aircraft by the heat they radiate–has been developed by researchers at General Electric (GE) Co.
‘s Research and Development Center in Schenectady, N.Y. Its charge-injection device technology is based on the silicon sensors that led to GE’s solid-state television cameras. In the new device, indium antimonide replaces silicon, shifting the chip’s spectral sensitivity into the 3 to 5 micron IR range. Though 1,024 pairs of metal-insulated semiconductor capacitors share a chip just 0.116 inch by 0.318 inch, placing a lens in front of it enables the device to image a large area in detail, according to Ching-Yeu Wei, its primary developer.
Two capacitors form each energy-gathering pixel. One picks up the faint IR signal, storing it as an electric charge. For the chip to report that signal, the charge must be transferred to a readout capacitor. To double or more the charge-transfer efficiency of this chip–and with that, its sensitivity–each capacitor duo has been designed as a concentric ring instead of a side-by-side pair. Also aiding efficiency is its planar topography; the usual deep etched hills and valleys can sometimes trap a charge and prevent it from transferring, Wei notes.