Colloidal quantum dot (CQD)-based photodetectors are promising alternatives to bulk semiconductor-based detectors to be monolithically integrated with complementary metal-oxide semiconductor readout integrated circuits avoiding high-cost epitaxial growth methods and complicated flip-bonding processes. To date, photovoltaic (PV) single-pixel detectors have led to the best performance with background-limit infrared photodetection performance. However, the nonuniform and uncontrollable doping methods and complex device configuration restrict the focal plane array (FPA) imagers to operate in PV mode. Here, we propose a controllable in situ electric field-activated doping method to construct lateral p-n junctions in the short-wave infrared (SWIR) mercury telluride (HgTe) CQD-based photodetectors with a simple planar configuration. The planar p-n junction FPA imagers with 640 × 512 pixels (15-μm pixel pitch) are fabricated and exhibit substantially improved performance compared with photoconductor imagers before activation. High-resolution SWIR infrared imaging is demonstrated with great potential for various applications including semiconductor inspection, food safety, and chemical analysis.