The graded bandgap multilayer avalanche photodiode: A new low-noise detector

We propose a new multistage avalanche photodiode for low-noise optical detection. In each stage, the ionization energy is provided by a heterointerface conduction-band step. Thus, ideally, only electrons cause ionization, and the device mimics a photomultiplier. This detector has intrinsically lower noise and lower operating voltage than conventional avalanche detectors. Designs for 1.3 µm fiber optic systems are presented and possible realizations using molecular beam epitaxy discussed.