An avalanche photo-transistor device , the device comprising: a detection region configured to: absorb light incident on a first surface of the detection region; and generate one or more charge carriers in response to absorbing the incident light; a first terminal in electrical contact with the detection region and configured to bias the detection region ; an intermediate doping region having a doping concentration of a first type dopant that is greater than a threshold doping concentration, wherein the one or more charge carriers flow toward the intermediate doping region ; a second terminal in electrical contact with the intermediate doping region and configured to bias the intermediate doping region ; a multiplication region configured to: receive the one or more charge carriers flowing from the intermediate doping region ; and generate one or more additional charge carriers in response to receiving the one or more charge carriers; and a third terminal in electrical contact with the multiplication region and configured to bias the multiplication region , wherein the intermediate doping region is located in between the detection region and the multiplication region , characterized in that the avalanche photo-transistor device is a laterally-integrated avalanche photo-transistor device in which a flow of charge carriers generated within the detection region and of additional charge carriers generated within the multiplication region is lateral with respect to a light incident top surface of the device. a detection region configured to: absorb light incident on a first surface of the detection region; and generate one or more charge carriers in response to absorbing the incident light; absorb light incident on a first surface of the detection region; and generate one or more charge carriers in response to absorbing the incident light; a first terminal in electrical contact with the detection region and configured to bias the detection region ; an intermediate doping region having a doping concentration of a first type dopant that is greater than a threshold doping concentration, wherein the one or more charge carriers flow toward the intermediate doping region ; a second terminal in electrical contact with the intermediate doping region and configured to bias the intermediate doping region ; a multiplication region configured to: receive the one or more charge carriers flowing from the intermediate doping region ; and generate one or more additional charge carriers in response to receiving the one or more charge carriers; and receive the one or more charge carriers flowing from the intermediate doping region ; and generate one or more additional charge carriers in response to receiving the one or more charge carriers; and a third terminal in electrical contact with the multiplication region and configured to bias the multiplication region , wherein the intermediate doping region is located in between the detection region and the multiplication region , characterized in that the avalanche photo-transistor device is a laterally-integrated avalanche photo-transistor device in which a flow of charge carriers generated within the detection region and of additional charge carriers generated within the multiplication region is lateral with respect to a light incident top surface of the device. <EOS>