Ultrahigh-sensitivity far infrared photodetectors by using the quantum Hall effect

When a two-dimensional electron system (2des) is subjected to a strong magnetic field at lowtemperatures,the motion of electrons are completely quantized by cyclotron motion and O-dimensional like，equi-distant energy levels (Landau levels) are formed. In such a situationa novel phenomenon called the quantum Hall effect appears Although the quantum Hall effect通常适用于resistance standardswe are pursuing a possibility of using QHE for the detection of far infrared radiation （or sometimes）called terahertz radiation . The major results of this project are；(1) we have found that the diagonal resistance of the 2 des exhibits a very large photosensitivity inthe vicinity of the quantum Hall states. From the analysis of the excitation spectra这是明确的，photosensitivity是induced by cyclotron resonance absorption and thatthere are two mechanisms in the process, i.e.，(i) electron heating due to photoabsorption和（ii） modulation of edge channel transport throughpotential redistribution by spatial separation of photoexcited electron and holes.(2) TheQHE detector increases linearly with increasing the bias current and reachesD17 D1 V/W，这是1000 times larger than that of conventional bolometers. Further increase of the bias(3)我们已经发现了，在反应中的反应。dominant noise of the QHE detector is the 1/f noise and that it increases very quickly withincreasing the bias current. Consequently，the maximum detectivity was obtained at relatively low bias currents (-μA).(4) the overalldetectivity of the QHE photodetector was estimated to be 3x10 wid113 wid11 /2 wid1cm /W，which is approximately 50 times larger than that of conventional bolometers. This high detectivityindicates the superiority of the QHE photodetector as ultirahigh-sensitivity far infraredphotodetector。

When a two-dimensional electron system (2DES) is subjected to a strong magnetic field at low temperatures, the motion of electrons are completely quantized by cyclotron motion and O-dimensional like, equi-distant energy levels (Landau levels) are formed. In such a situation, a novel phenomenon called the quantum Hall effect appears. Although the quantum Hall effect (QHE) is most often applied to resistance standards, we are pursuing a possibility of using QHE for the detection of far infrared radiation (or sometimes called terahertz radiation). The major results of this project are ;(1) We have found that the diagonal resistance of the 2DES exhibits a very large photosensitivity in the vicinity of the quantum Hall states. From the analysis of the excitation spectra, it is clarified that the photosensitivity is induced by the cyclotron resonance absorption and that there are two mechanisms in the process, i. e., (i) electron heating due to photoabsorption and (ii) modulation of edge channel transport through potential redistribution by spatial separation of photoexcited electron and holes.(2) The responsivity of the QHE detector increases linearly with increasing the bias current and reaches 10ィイD17ィエD1 V/W, which is 1000 times larger than that of conventional bolometers. Further increase of the bias current results in the reduction in responsivity due to joule heating.(3) We have found that the dominant noise of the QHE detector is the 1/f noise and that it increases very quickly with increasing the bias current. Consequently, the maximum detectivity was obtained at relatively low bias currents (-μA).(4) The overall detectivity of the QHE photodetector was estimated to be 3x10ィイD113ィエD1 HzィイD11/2ィエD1cm/W, which is approximately 50 times larger than that of conventional bolometers. This high detectivity indicates the superiority of the QHE photodetector as a ultirahigh-sensitivity far infrared photodetector.