Development of an ultra-sensitive far-infrared detector based on double quantum-well structure

摘要

We are developing an ultra-sensitive far-infrared detector for astronomy as an application of CSIPs -Charge Sensitive Infrared Phototransistors. The CSIPs is fabricated in GaAs/AIGaAs double quantum-well structure (Fig.1). The detection principle of CSIPs is that the upper quantum-well (QW) as a floating gate is charged up by photo-absorption between inter-subbands of the QW, and the conductance of the lower QW is increased as the result of the charge up of the gate. We measure the change of current as a function of photon flux. The great advantage of CSIPs is the huge gain of current amplification, so that the noise performance is not limited by the readout noise. CSIPs are well established for mid-infrared photons, shorter than 30 μm in wavelength. The noise equivalent power (NEP) of CSIPs is achieved 2×10~(-19) [W Hz~(-1/2)] at 15 μm with the Quantum efficiency of 7%.