The researchers say that by varying the applied bias voltage the device can detect different infrared wavebands. This could open up a range of potential applications, including infrared colour televisions and three-color infrared imaging.
Prof Razeghi explained: "A device capable of detecting different infrared wavebands is highly desirable in the next generation infrared imaging systems."
The researchers invented and investigated their design for three-colour photodiodes without using additional terminal contacts. The resulting photodetector is based on indium-arsenide/gallium-antimonide/aluminium-antimonide type-II superlattices.
As the applied bias voltage varies, the photodetector sequentially exhibits the behaviour of three different colours, corresponding to the bandgap of three absorbers, and is said to achieve well-defined cut-off wavelengths and high-quantum efficiency in each channel.
This research builds on the group's previous work in Northwestern's Centre for Quantum Devices, including the development of the first single-colour, short-wavelength infrared photodetector and two-colour, shortwave-midwave infrared photodetector based on type-II superlattices.
"I am fascinated by these results," Prof Razeghi said. "The initial success in this demonstration will drive us to the new frontier of infrared detection and imaging technology."
