Light-emitting transistor: Light emission from InGaP/GaAs heterojunction bipolar transistors

This letter reports the direct observation of the radiative recombination in the graded base layer of InGaP/GaAs heterojunction bipolar transistors (HBTs). For a 1 μm×16 μm emitter HBT, we demonstrate the change of the spontaneous light emission intensity (ΔIout) as the base current (Δib) of the HBT is varied from 0 to 5 mA, i.e., an HBT operating as a light-emitting transistor. We also demonstrate output light modulation from the base layer at 1 MHz with the base current modulated at 1 MHz in normal transistor mode operation of the HBT.