Research Of Silicon-based Near-infrared Photodetector With Pb-based Quantum Dots

As a great invention in the 20th century,the transistor has changed the lifestyle of human beings.The photoelectric devices based on silicon technology have rapidly occupied most of the electronic market with the advantages of low cost,low power consumption,and easy large-scale integration,which are widely used in the fields of imaging and detection in the visible spectrum.With the advancement and development of material technology,the emerging"zero-dimensional"quantum dots have become a research hotspot in the field of photodetection in recent years.The typical representatives of quantum dot materials with absorption peaks in the near-infrared band are Pb S and Pb Se quantum dots which are widely investigated for their advantages such as large Bohr radius,low cost,easy synthesis,and the potential to be deposited on any substrate.Quantum dots exhibit unique optoelectronic properties due to their extremely small size in three dimensions,such as quantum size effect,surface effect,and multiple exciton generation effects.These features are well suitable for integration with mature silicon-based devices that can be applied in silicon-based infrared photoelectric detection.In this dissertation,the Pb S quantum dot and the structure of silicon-based optoelectronic devices will be studied.The semiconductor process simulation&device simulation software,TCAD,will be used to design silicon-based quantum dot optoelectronic devices and investigate the detection mechanism as well as the structural parameters of the devices.In the experiments,the performance of Pb S quantum dot silicon-based photodetectors is prepared and investigated using mature and controllable Pb S quantum dot materials combined with silicon epitaxial substrates.Pb Se quantum dots with different first exciton absorption peaks were synthesized by the thermal injection method,and silicon-based quantum dot photodetectors with spectral selectivity were fabricated.Finally,the 1×64 linearized silicon-based quantum dot photodetectors were fabricated by combining simulation and experimental conclusions,for which the optoelectronic properties of the devices were systematically investigated.The research in this dissertation can be summarized in the following four sections.1.The photodetector of a silicon-based quantum dot hybrid structure is investigated based on the Sentaurus TCAD semiconductor simulation software.The detection mechanism and gain of photovoltaic field-effect transistor structures are analysed through theoretical simulations,and the effects of different structural parameters and doping of materials on device performance are investigated.In conjunction with the Sentaurus Device physical properties simulation tool,the intrinsic mechanism of the response current variation of the photodetector is analysed,which provides useful parameters for the following experiments.The simulation results indicate that the width of the depletion layer between the channel and the substrate decreases with increasing doping concentration;the smaller the channel length,the higher the responsivity and EQE of the device.The maximum responsivity of the simulated device reaches 2.75×10³ A/W,with a corresponding D*of 3.58×10¹² Jones and a high EQE of 8577.6%.2.We investigated silicon-based photodetectors with Pb S colloidal quantum dots and designed a novel junction-type field-effect transistor detection structure,which effectively balances traditional quantum dot materials with the difficulty of achieving high responsivity and fast response time simultaneously.The effect of band alignment of the photosensitive layer on the response time of the device is investigated,and the cut-off wavelength of the silicon-based photodetector is finally extended in order to achieve the co-existence of high responsivity and fast response time.The devices are prepared by a room-temperature solution method and are therefore easy to integrate.Pb S quantum dot silicon-based photodetectors with the addition of a Pb S-EDT layer exhibit a low response time of 211/558μs for incident light at 808 nm.Since the absorption range of Pb S colloidal quantum dots covers visible light to near-infrared,the device responds to incident light from 405 nm to 1550 nm and exhibits a broad spectral response,with a maximum responsivity of 1615 A/W and external quantum efficiency EQE and D*reaching 4.96×10⁵%and 3.95×10¹² Jones respectively.3.We present a spectrum-selective photodetector based on the adjustable bandgap of quantum dots.We innovatively propose and verify the integration of the spectrum-selective capability directly onto a single unit,which solves the influence of the visible light on the infrared detection performance,and simplifies the complex optical-mechanical structure in infrared detection systems.The device successfully achieves a high selectivity factor of at least one order of magnitude higher than that of the non-target light detection.The selective photodetector achieves a responsivity of 613 A/W at 1550nm in the communication band,corresponding to an EQE and D*of 5.02×10³%and4.8×10¹⁰ Jones,respectively.At the same time,the addition of the filter layer did not affect the response time of the device,which was as low as 37.9/92.3μs at 1550 nm.The optical measurements of the small-sized colloidal quantum dot film used as the filter layer were carried out to calculate the transmission characteristics of the thickness for different wavelengths of the incident light,providing a theoretical basis for the preparation of the filter layer for practical devices.4.Based on the aforementioned device simulation and a single device research foundation,the feasibility of a line array device is investigated.In order to verify the feasibility of coupling low-dimensional quantum dots with silicon-based devices,a silicon-based quantum dot photodetector with a line array size of 1×64 is designed for the first time,which provides a certain value for the development of one-chip integrated array devices.