Low dark current and high dynamic range a-Si:H MSM photodetector for large area medical imaging

Sina Ghanbarzadeh, Shiva Abbaszadeh, Michael Adachi, Karim S. Karim

Research output: Chapter in Book/Report/Conference proceedingConference contribution


Metal-Semiconductor-Metal (MSM) photodetectors are attractive as sensors due to their ease of fabrication and compatibility with thin film transistor fabrication process primarily because there is no P+ doped layer. We report an a- Si:H MSM lateral structure with low dark current, high dynamic range and comparable sensitivity to conventional p-i-n photodiodes. These improvements are achieved by the introduction of a thin polymer layer as a blocking contact. The fabricated amorphous silicon based MSM detector exhibits a photo-response of more than 3 orders of magnitude to a green light source (λ = 525nm) with intensity of 73μW/cm2. In comparison to vertical p-i-n structures, the reported MSM lateral devices show gains in terms of dynamic range, ease of fabrication (no p+ layer), and faster speed at the cost of slightly reduced responsivity. The experimental results of dark and photocurrent measurements as well as the responsivity for two in-house fabricated MSM structures at different bias voltages and light intensity are presented. This results are promising and encourage the development of a-Si:H lateral MSM devices for indirect conversion large area medical imaging applications and especially low cost flat panel computed tomography.

Original languageEnglish (US)
Title of host publicationMedical Imaging 2013
Subtitle of host publicationPhysics of Medical Imaging
StatePublished - Jun 3 2013
EventMedical Imaging 2013: Physics of Medical Imaging - Lake Buena Vista, FL, United States
Duration: Feb 11 2013Feb 14 2013

Publication series

NameProgress in Biomedical Optics and Imaging - Proceedings of SPIE
ISSN (Print)1605-7422


OtherMedical Imaging 2013: Physics of Medical Imaging
CountryUnited States
CityLake Buena Vista, FL


  • Amorphous SI
  • Dark current
  • Indirect conversion
  • MSM photodetectors
  • X-ray imaging

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Biomaterials
  • Atomic and Molecular Physics, and Optics
  • Radiology Nuclear Medicine and imaging

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