A Simulation Sdudy Of Si-PIN Photodetector Based On Nanoimprint Lithography

Silicon is the most commonly used material in semiconductor industry because it is easily purified and doped, and the associated fabrication technology has developed for decades. However, the sensitivity and efficiency of silicon-based photodetectors are limited by two factors, one is that crystal silicon surfaces perform highly light reflection across the electromagnetic spectrum, and the other is that silicon material has a direct band gap in its electronic structure. With the development of optoelectronic devices, the application of nanoscale photonics is becoming deeper and wider. The feature size of optoelectronic devices becomes smaller and smaller, the pattern complexity also increases gradually. As one of the most promising methods in the next-generation lithography,nanoimprint lithography(NIL) attracts great attention nowadays. NIL, with its advantages of low cost, better resolution, high efficiency and elevated flexibility, has become one of the most promising research interests in micro and nano fabrication. Based on this understanding, this thesis has carried out a simulation study on the Si-PIN photodetector which light absorbing surface was etched by NIL.This thesis has made full use of the so-called microstructured silicon surface and the energy engineering of nanoporous silicon pillar array, and carried out a simulation study of a novel Si-PIN photodetector based on nanoporous silicon pillar array. The knowledge of semiconductor and device physics are used to design the structure of the photodetector. And a simulation software named Silvaco TCAD is chosen to study the performance of the device, such as spectral response, quantum efficiency, light responsivity, I-V characteristics, dark current and response time, respectively. The results could provide a guidance for the actual processing of the new photodetectors.The performance of the Si-PIN photodetector based on nanoporous silicon pillar array silicon with modified energy engineering shows:(1) that compared with the conventional photodetector, the peak wavelength can be red-shift a little and the quantum efficiency and responsivity of the front illuminated detector at peak wavelength(1100nm) are 43.80% and 0.39A/W, while at 1060 nm are 42.11% and 0.36A/W, respectively.(2) that the dark current and response time of the front illuminated detector are 0.54 nA and 7ns, respectively, which are the same as those of conventional photodetectors.Furthermore, this thesis has tried to develop a new type of Si-PIN photodetector based on nanoporous silicon pillar array with modified energy engineering, and carried out an actual manufacture on it through a foundry. We have carried out the NIL etching on top of p layer. Our preliminary studies indicate that the responsivity of the new Si-PIN photodetector based on nanoporous silicon pillar array has been obviously improved in the range of visible to near infrared(400nm~1100nm), in which the responsivity at 1060 nm is increased by 0.25 A/W at the rate of 67%, compared to the conventional photodetector.