Charge-Sensitive Infrared Phototransisotrs: Ultra-sensitive Detectors in the Wavelength Range of 5-50µm

Novel ultrasensitive detectors in the wavelength range of λ = 5-50 μm have developed. The detectors are charge-sensitive infrared phototransistors (CSIPs) fabricated in GaAs/AlGaAs double quantum well structures. The devices serve as a phototransistor capable of counting single photons, while a function is similarly to CMOS image sensors. The excellent noise equivalent power (NEP = 6.8x10-19 W/Hz^1/2) and specific detectivity (D* = 1.2 x 10¹⁵ cmHz^1/2/W) are demonstrated for λ = 14.7 μm, which are by a few orders of magnitude superior to those of the other state-of-the-art detectors. These figures of merit persist up to 23K. Temperature dependence of the performance is studied and wavelength range expansion is attempted. The simple planar structure of CSIPs is feasible for array fabrication including future monolithic integration with reading circuits.