Monolithic integrated InGaAlAs/InP ridge waveguide photodiodes for 1.55 μm operation grown by molecular beam epitaxy

The monolithic integration of a low loss InGaAlAs ridge waveguide with a low leakage InGaAs photodiode is demonstrated. The structure has been grown by molecular beam epitaxy on an n+-InP substrate, using an InGaAlAs layer with a band gap of 1.29 μm, suitable for waveguiding at 1.55 μm wavelength. Absorption of the guided light is provided by leaky coupling from the InGaAlAs guiding layer into the higher index InGaAs absorbing region containing a p/n junction. The devices showed external quantum efficiencies as high as 20% for operation at 1.55 μm wavelength. This is the first demonstration of a monolithic integrated waveguide device in the InGaAlAs/InP material system.