Low photocurrent GaAs-Al/sub 0.3/Ga/sub 0.7/As multiple-quantum-well modulators with selective erbium doping

A new scheme of reducing the photocurrent of a quantum-confined Stark effect multiple-quantum-well modulator is demonstrated. The GaAs well regions of the 50-period GaAs-Al/sub 0.3/Ga/sub 0.7/As multiple-quantum-well are selectively doped with Er during molecular beam epitaxy to reduce the carrier lifetime to the order of picoseconds. 250-μm diameter mesa-shaped devices have been characterized. The photocurrent responsivity is as low as 0.005 A/W and an extinction ratio greater than 1:8 is achieved at a bias voltage of 8 V.