A two-color infrared detector using GaAs/A]GaAs and strained InGaAs/Al
GaAs multiquantum wells is demonstrated. The response peak of the GaAs
/AlGaAs quantum well is at 8 mum, and that of the InGaAs/AlGaAs quantu
m well is at 5.3 mum. The responsivity of the detector is 1 A/W at 8 m
um and 0.27 A/W at 5.3 mum; these are the best values reported for a t
wo-color quantum well infrared detectors (QWIPs) with peak sensitiviti
es in the spectral regions of 3-5.3 mum and 7.5-14 mum. Single-colored
5.3 and 8 mum QWIPs were also fabricated to study the bias dependent
behavior. This behavior can be explained using the concept of current
continuity. Because of a higher electrical resistance, a high electric
field domain is always formed first in the shorter wavelength quantum
well stack.