640×480 pixel active-matrix HEED imaging sensor with HARP target

In this paper, an active-matrix planar-type cold electron emitter array development is studied to fulfill the requirement of high-speed response. This emitter array adopts a novel MIS emitter which is termed HEED (High-efficiency Electron Emission Device) and fabricated on a MOS transistor array formed on a silicon wafer with scan driver circuits. HEED´s driving voltage is relatively low (about 20V) and its MIS structure is compatible with silicon planar processing employed for LSI. As a consequence, The HEED is one of the most suitable emitters for an active-matrix drive configuration. The emission current density (defined as the average pixel current per emitter area size) reaches up to 4.4 A/cm . This highly emissive property fulfills the imaging requirement of a HARP target. The specifications of the active-matrix HEED are summarized. The number of the interconnections to drive this chip is applicatory 12 lines. This is another important advantage of the active-matrix drive method.