Improved electrical properties of Ga2O3:Sn/CIGS hetero-junction photoconductor

Kenji Kikuchi, Shigeyuki Imura, Kazunori Miyakawa, Hiroshi Ohtake, Misao Kubota, Eiji Ohta

Research output: Contribution to journalConference articlepeer-review


We examined the potential application of CuIn1-xGaxSe 1-ySy (CIGS) film for visible light image sensors. CIGS chalcopyrite semiconductors, which are representative of high efficiency thin film solar cells, have both a high absorption coefficient and high quantum efficiency. However, their dark current is too high for image sensors. In this study, we applied gallium oxide (Ga2O3) as a hole-blocking layer for CIGS thin film to reduce the dark current. The dark current of this hetero-junction was 10-9 A/cm2 at less than 7 V. Moreover, an avalanche multiplication phenomenon was observed at an applied voltage of over 8 V. However, this structure had sensitivity only in the ultraviolet light region due to the much lower carrier density of the Ga2O3 layer. We therefore used a tin-doped Ga2O3 (Ga 2O3:Sn) layer deposited by pulsed laser deposition (PLD) for the n-type layer to increase the carrier density. The sensitivity of the visible region was observed in the Ga2O3:Sn/CIGS hetero-junction. We also investigated the influence of the laser frequency of the PLD on the transmittance of Ga2O3:Sn and the quantum efficiency of this hetero-junction. Ga2O3:Sn film deposited at a 0.1-Hz laser repetition rate had higher transmittance than at a 10-Hz repetition rate. The Ga2O3:Sn/CIGS hetero-junction also had a higher quantum efficiency with the lower rate (50%) than with the higher rate (30%).

Original languageEnglish
JournalMaterials Research Society Symposium Proceedings
Publication statusPublished - 2014
Externally publishedYes
Event2013 MRS Fall Meeting - Boston, MA, United States
Duration: 2013 Dec 12013 Dec 6


  • photoconductivity
  • sensor
  • thin film

ASJC Scopus subject areas

  • General Materials Science
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering


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