Temperature dependence of the performance of charge-sensitive infrared phototransistors
ABSTRACT The performance of charge-sensitive infrared phototransistors ( λ∼14.7 μ m ) is studied at temperatures of up to 30 K. The devices, with a 16×4 μ m 2 photoactive area, are fabricated in GaAs/AlGaAs double-quantum-well structure. An excellent specific detectivity D*=9.6×1014 cm Hz 1/2/ W is derived in a T range of up to T=23 K . Experimental results are theoretically studied based on WKB approximation, in which photogenerated holes in the floating gate (FG) are recombined with thermal emission or thermally assisted tunneling from the outside of FG through the barriers. The model well reproduces the experimental results, including the vanishing of photosignal at 30 K under 280 fW incident radiation. The model is used to predict a temperature-dependent specific detectivity D* in ideal devices free from 1/f noise.
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ABSTRACT: 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.Sensors 01/2010; 10(9):8411-23. · 1.95 Impact Factor
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ABSTRACT: Semiconductor quantum dot detectors as well as semiconductor charge-sensitive infrared phototransistors are described. They are the only detectors that can count single photons in the terahertz region at present. In terms of the noise equivalent power (NEP), the detectors realize experimental values on the order of 10<sup>-21</sup> W/Hz<sup>1/2</sup>, while theoretically expected values are even much lower, on the order of 10<sup>-24</sup> W/Hz<sup>1/2</sup>. These NEP values are by several orders of magnitude lower than any other state-of-the-art highly sensitive detectors. In addition to the outstanding sensitivity, the detectors are featured by strong advantage of huge current responsivity (10<sup>6</sup>-10<sup>10</sup> A/W ) and extremely large dynamic range of response (10<sup>6</sup>-10<sup>8</sup>). The mechanism of detection as well as application of the detectors is discussed.IEEE Journal of Selected Topics in Quantum Electronics 03/2011; · 4.08 Impact Factor