Schottky contact infrared sensors operates in near (NIR) and short wavelength IR (SWIR) ranges (1-5 ?m). Ranges of the near and short wavelength infrared radiation (NIR and SWIR) (1-5 ?m) are very important for different space exploration missions. 1-3 ?m wavelength IR radiation range is very important for satellite based observation of the land-water boundaries, metereological studies, observation of the forest fires and lawa flows as well as for estimation how much water is present in plants and soil. IR sensors operating in 1-3 ?m wavelength are applied for geological (mineralogical) investigations of the surface of the planets as well as for studies of the atmospheric phenomena in other planets. Photosensors operating in 3-5 ?m wavelength range are most often used to study Earts thermal radiation in the dark of night.
In Schottky sensors minimum energy of the absorbed photon is limited by Schottky barrier height. Therefore subbandgap photons can be detected. Thus silicon can be used for fabrication of these sensors instead of the narrow bandgap semiconductors such as Ge or CdHgTe. Therefore main project idea is design, fabrication and investigations of the advanced Schottky IR photosensor. Main problem of the Schottky IR sensors is as follows. Probability of the photoemission from the metal to the semiconductor increase with metal layer thickness. However it results in decreased absorbance of the photons. In suggested project graphene would be used as Schottky contact metal. That is is monolayer of the hexagonal sp2 bonded carbon. Due to the 0 eV bandgap graphene is excellent Schottky contact material. There is no free electron scattering problem in graphene. Therefore most of the photoenerated charge carriers can reach junction at appropriate angles and flow to the Si. Metal film of such thickness would be non-continuous.
Relatively small absorbance of NIR and SWIR photons in graphene in present study will be compensated by fabrication of the ultra-thin (thickness smaller than electron free path) nanostructured plasmonic absorbers. Photon will be absorbed and photoelectrons will be generated in these absorbers. These processes will be enhanced by surface plasmon resonance.
Hot plasmonic electrons will be injected to the graphene. Afterwards these electrons will be emitted to the Si along with photoelectrons generated in graphene.
Project goal – fabrication and investigations of the novel near and short wavelength infrared subbandgap Schottky photosensors operating by emission of the plasmonic
European Space Agency (ESA) Programme for European Cooperating States (PECS)
Period of project implementation: 2017-09-04 - 2020-04-30
Project coordinator: The European Space Agency
Project partners: Kaunas University of Technology, The European Space Research and Technology Centre