An image sensor consisting of an active-matrix high-efficiency electron emission device (HEED) array and a high-gain avalanche rushing amorphous photoconductor (HARP) has been fabricated. Based on the demonstration that a prototyped 256 X 192 pixel image sensor can pick up a high definition image with an ultrahigh sensitivity under poor light condition, the authors have been developing a 640 X 480 pixel active-matrix HEED toward a practical use. The emission current density has been enhanced more than twice compared to that of previous one and has increased up to 1 A/cm(2). The active-matrix HEED array combined with HARP is available for application to practical image sensing with an ultrahigh sensitivity and high definition. (c) 2007 American Vacuum Society.