InGaAs pin photodiodes on recessed semi-insulating GaAs substrates

Low leakage current Ga1¿xInxAs pin photodiodes have been fabricated on GaAs substrates by incorporating an GaAs/Ga1¿xInxAs superlattice buffer to accommodate the lattice mismatch. Devices fabricated from Ga0.65In0.35As on n+ substrates exhibited leakage currents below 1 nA at ¿10 V, and external uncoated quantum efficiencies of ~47% at 1.15 ¿m. A growth and processing sequence for fabricating devices in recesses on semi-insulating GaAs substrates with a coplanar geometry, to allow subsequent GaAs circuit processing, has been identified, and shown not to introduce a significant leakage penalty.