A method for providing and operating a device in a first mode as a light-emitting transistor and in a second mode as a high speed electrical transistor, including the following steps: providing a semiconductor base region of a first conductivity type between semiconductor emitter and collector regions of a second semiconductor type; providing, in the base region, a quantum size region; providing, in the base region between the quantum size region and the collector region, a carrier transition region; applying a controllable bias voltage with respect to the base and collector regions to control depletion of carriers in at least the carrier transition region; and applying signals with respect to the emitter, base, and collector regions to operate the device as either a light-emitting transistor or a high speed electrical transistor, depending on the controlled bias signal.