Low Light Level Readout Of Quantum Dots Photodetector And Application Research

Low-light-level detection systems play an important role in medical diagnosis, bio-molecular sciences, environmental monitoring, and military reconnaissance. Quantum dots photodetector developed in recent years have an advantage of low operating voltage, high sensitivity and room temperature operation due to high carrier confinement by quantum dot, enabling it to be one of the hot research topics in low-light-level detection systems.The dissertation mainly mainly focused on light characteristics and readout of 64 pixels quantum dots photodetector, and explore the application of micro-spectrometer and microscopical imaging spectrometer as well. The main contents of the dissertation are as follows:(1) Research has been conducted on high sensitivity characteristics of quantum dots photodetector. By optimizing the test condition, the low-light-level can be effectively lowered to 0.01 picowatts power. The photocurrent is 1.2×10-8 A and the photocurrent responsivity is about 1.2×106 A/W when the photodetector is illuminated by 632.8 nm laser at 0.01 picowatts power with-0.5 V bias voltage at room temperature. In another case, the photocurrent is 5.69×10-7 A and photocurrent responsivity is about 5.69×107 A/W when the photodetector is subjected to 0.01 picowatts power and -3 V bias voltage at 77 K.(2) An equivalent modeling approach is proposed and simple model has been constructed. Experimental results show that the simulation curves and parameters agree very well with the experimental results. The 0.01 picowatts power focused laser has been readout based on readout circuits and 64 pixels photodetector array. The 7 mV response voltage is achievable under 80.4μs integration duration and -0.5 V bias, wherein the photodetector is illuminated by 0.01 picowatts,632.8 nm He-Ne laser at room temperature. The voltage responsivity is 7×1011 V/W.(3) A nonuniformity calibration method based on 64 pixels quantum dots photodetector is proposed. The calibrated spectrum curves of micro-spectrometer based on quantum dots photodetector are consistent with scientific-grade spectrometer.(4) Spectra of biological samples has been studied based on the quantum dot micro-spectrometer and microscopy hyperspectral imaging system, the experimental results show that the biological sample transmittance spectra obtained by the two spectral measurement systems are well coincided.(5) A test of luminescent liquid sample is taken for further sensitivity analysis. The quantum dot photodetector spectrometer shows higher sensitivity, compared to the CCD spectrometer.