Integrated multijunction GaAs photodetector with high output voltage

Integrated structures consisting of two P-I-N double heterostructure GaAs photodetectors, series connected by means of a tunnel junction, have been fabricated by molecular beam epitaxy. Open-circuit output voltages, external power efficiencies, and fill factors were 1.777 V, 33.4%, and 0.83, respectively, for antireflection-coated cells excited by ∼5 mW optical power from a focused DH AlGaAs laser emitting at λ=0.815 μm.