Semiconductor avalanche photo transistors and methods of manufacturing the same, operable for internal amplification of a photo signal and for use in detection of weak light signals, gamma rays and nuclear particles. The multi-pixel avalanche photo transistor devices can comprise a semiconductor layer, a plurality of semiconductor areas (pixels) forming a p-n-junction with the semiconductor layer, a common conductive grid separated from the semiconductor layer by a dielectric layer and individual micro-resistors connected to said semiconductor areas with the common conductive grid. Systems and methods described can be operable to decrease optical crosstalk at high signal amplification and the special capacity of the multi-pixel avalanche photo transistor, as well as improve speed of its photo response.