PbS colloidal quantum dots based photodetectors for integrated SWIR detection
Heves, Emre (2012) PbS colloidal quantum dots based photodetectors for integrated SWIR detection. [Thesis]
Official URL: http://192.168.1.20/record=b1488913 (Table of Contents)
Due to the low water absorption and nightglow, sensing in short wave infrared (SWIR) is very attractive in applications such as; passive night vision, biomedical imaging and remote sensing. The monolithic integration of photodetectors to the readout circuits is desirable in many applications to increase density of detectors and reduce costs, system size and power consumption. Solution-processed semiconductors are a promising alternative to conventional bulk crystalline photodetectors since their production is low cost and easy, their bandgap can be tuned depending on their sizes, and they can be easily integrated on any substrate. In this work, PbS colloidal quantum dot based photodiodes are realized that are compatible with the integration on Read Out Integrated Circuits (ROIC). Various kinds of PbS quantum dots based schottky diodes are designed on glass and silicon substrates. Spin deposition steps and solid state ligand exchange processes are optimized to create pinhole free and high mobility PbS quantum dot layers. In addition to that Integrated Circuit (IC) compatible versions of PbS colloidal quantum dot (CQD) photodiodes are realized. ROIC chip surface is mimicked on Si substrates and fabrication steps are optimized for integration. Special importance is given to optimize highly conductive and transparent indium tin oxide layer using DC magnetron sputtering. Sensitivities of 1.4x1012 Jones, comparable to the conventionally used crystalline, bulk photodetectors is achieved. Also, plasmonic scattering effects of metal nanoparticles in PbS CQD layer are studied. Absorption and responsivity enhancement of 6 fold is presented using gold nanoparticles in PbS CQD based photoconductors.
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