Characterization of optically sensitive amorphous selenium photodetector at high electric fields

Saeedeh Ghaffari, Shiva Abbaszadeh, Sina Ghanbarzadeh, Karim S. Karim

Research output: Contribution to journalArticlepeer-review


We investigated the electrical conduction in indium tin oxide/polyimide (PI)/amorphous selenium/Au device structures, operated at high fields (up to 40 V/μm). Devices having different PI thicknesses (0.4-2.5 μm) with the same thickness of a-Se (16 μm) were fabricated, and the dark and photocurrent transient behavior of each device under different biasing voltages was tested. The results indicate that an optimal thickness of PI (∼ 1 μm) was necessary to limit the dark current to below 10 pA/mm2 while achieving an on/off ratio of 104, a result not achievable in devices without the PI layer. Furthermore, time-of-flight (TOF) measurements at low electric fields (∼ 10 V/μm) were carried out to measure the exact voltage drop within the PI and a-Se films for the same structure. Based on these TOF measurements, the electric field within the PI layer was determined to reach 138 V/μm to provide efficient electrical conduction for photogenerated electrons.

Original languageEnglish (US)
Article number7118668
Pages (from-to)2364-2366
Number of pages3
JournalIEEE Transactions on Electron Devices
Issue number7
StatePublished - Jul 1 2015
Externally publishedYes


  • Amorphous selenium (a-Se)
  • optical detectors
  • polyimide (PI)
  • time of flight (TOF)

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Electrical and Electronic Engineering


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