An active-matrix array of high-efficiency electron emission device (HEED) with a sufficient output density has been developed for the use as imaging probe in a high-gain avalanche rushing amorphous photoconductor target. Previously, it was demonstrated that a prototyped image sensor with 20 X 20 mu m(2) pixels could pick up a high definition image with an ultrahigh sensitivity under low-light-level condition. Based on it, an efficient active-matrix HEED with 13.75 X 13.75 mu m(2) pixels is fabricated for pursuing higher sensitivity and resolution. The improvement in the device isolation method enables to enlarge the relative emitting area, and then the emission current density per pixel reaches 3.6 A/cm(2) that is about four times of that obtained from the previous one. The active-matrix HEED array with small pixels is available for application to the compact ultrahigh-sensitivity image sensor without affecting on the image definition. (C) 2009 American Vacuum Society. [DOI: 10.1116/1.3079653]