High-speed and low-dark-current flip-chip InAlAs/InAlGaAs quaternary well superlattice APDs with 120 GHz gain-bandwidth product

High-speed flip-chip InAlAs/InAlGaAs quaternary well superlattice avalanche photodiodes grown by gas-source molecular beam epitaxy have been achieved with 120-GHz gain-bandwidth product. These photodiodes exhibit a maximum bandwidth of 15 GHz, 0.34- mu A dark current at a multiplication factor of 20, a capacitance of 0.17 pF, 65% quantum efficiency, and a low breakdown voltage of about 20 V. A clear eye opening at a multiplication factor of 20 was obtained for 10-Gbs nonreturn to zero signals. This indicates that these devices have potential for high-speed, high-sensitivity and low-power-consumption, long-wavelength optical receivers.>