Novel Ultra-Sensitive Detectors in the 10–50 μm Wavelength Range

We have developed novel single-photon detectors in the 10-50 μm wavelength region. The detectors are charge-sensitive infrared phototransistors (CSIPs) fabricated in GaAs/AlGaAs double quantum well (QW) structures, in which a photo-generated hole (+e) in the floating gate (upper QW) modulates the conductance of a capacitively-coupled channel located underneath (lower QW). The excellent noise equivalent power (NEP = 8.3 × 10(-19) W/Hz(1/2)) and specific detectivity (D(*) = 8 × 10(14) cm Hz(1/2)/W) are demonstrated for 15 micron detection up to 23 K, which are by a few orders of magnitude better than those of other state-of-the-art high-sensitivity detectors. The dynamic range exceeds 10(6) (~aW to pW) by repeatedly resetting the accumulated holes in the upper QW. Simple device structure makes the detectors feasible for array fabrication: Furthermore, monolithic integration with reading circuits will be possible.