High-performance substrate-removed InGaAs Schottky photodetectors

High-performance, vertical In/sub 0.53/Ga/sub 0.47/As Schottky diodes are demonstrated. An InP-substrate removal process exposes the underlying surface of lattice-matched epitaxial layers. The newly exposed surface facilitates ohmic contact and simplifies alignment of the optical input to the active detector area. The new process results in low dark current (I/sub d/<5 pA/μ²) and high responsivity (R>0.70 A/W). A dual-depletion design is utilized in the active layers of the detector resulting in reduced parallel plate capacitance per unit area. Reduced parallel plate and parasitic capacitance results in high bandwidth (f/sub 3 dB/>20 GHz) for 900-μm² detectors. Passivation of photodetectors with silicon dioxide is shown to reduce leakage currents by 50%.