We incorporated InGaAs quantum wells within the collector of InP-based heterojunction bipolar transistors to form novel light-modulating devices. We studied the properties of these devices as light modulators by direct current injection. The devices were characterized using differential photocurrent and transmission spectroscopies. Our results demonstrate the feasibility of light modulation based on current rather than electric field modulation. Maximum modulation is achieved when the accumulated carriers quench the excitonic absorption resonance.