Frequency division multiplexed dual-band infrared phototransistors for absolute temperature sensing

High-performance multispectral infrared photodetectors are essential for advanced imaging and sensing technologies. Here, we demonstrate a frequency division multiplexed (FDM) dual-band infrared phototransistor operating at 9.9 and 14.9 μm through a single source–drain channel. The device incorporates a double GaAs/AlGaAs quantum well (QW) structure, where two QWs of different thicknesses (7 and 11 nm) serve as charge-sensitive intersubband absorbers. Optical excitation at each wavelength induces opposite charge polarities on a floating gate, which are selectively demodulated by periodic resetting with distinct frequencies. This FDM operation enables simultaneous, independent readout of both spectral bands. Finally, we demonstrate absolute temperature sensing using the dual-band response, highlighting the device's potential for compact multispectral infrared sensing and imaging systems.