Abstract: Photosensitive semiconducting devices, such as bipolar junction transistors (BJTs) can be built up over a substrate that may include a read-out integrated circuit (ROIC). Semiconducting layers can be deposited over the substrate and bottom electrodes that are on or at the substrate's top surface. The bottom electrodes may be the input pads of the ROIC. A top electrode is deposited over the semiconducting layers. The semiconducting layers can form BJTs between the bottom electrodes and the top electrode. The top electrode and the bottom electrodes are the BJTs collectors and emitters. The semiconducting layers include a P-type quantum dot layer and a N-type metal oxide layer. The quantum dots act as light sensors for the ROIC because photons absorbed in a semiconducting layer can produce a BJT base current. The BJTs can be formed without requiring a vacuum or patterning of the top electrode.