Role of gate oxide in AlGaN/GaN high-electron-mobility transistor pH sensors

B. S. Kang, H. T. Wang, F. Ren, M. Hlad, B. P. Gila, C. R. Abernathy, S. J. Pearton, C. Li, Z. N. Low, J. Lin, J. W. Johnson, P. Rajagopal, J. C. Roberts, E. L. Piner, K. J. Linthicum

Research output: Contribution to journalArticlepeer-review

33 Scopus citations


We report on a comparison of different gate oxides for AlGaN/GaN high-electron-mobility transistor (HEMT) pH sensors. The HEMTs show a linear increase in drain-source current as the pH of the electrolyte solutions introduced to the gate region is decreased. Three different gate oxides were examined, namely the native oxide on the AlGaN surface, a UV-ozone-induced oxide and an Sc 2O 3 gate deposited by molecular beam epitaxy. The Sc 2O 3 produced superior results in terms of resolution in measuring small changes in pH. The devices with Sc 2O 3 in the gate region exhibited a linear change in current between pH 3 and 10 of 37 μA/pH with a resolution of <0.1 pH over the entire pH range. In contrast, the native oxide devices showed a larger change in current, ̃ 70 μA/pH, but with a degraded resolution of ̃ 0.4 pH. Results for the UV-ozone oxide were intermediate in resolution, 0.2 pH. These HEMTs have promise for detecting pH changes in biological samples and can be readily integrated into a standard package for wireless data transmission.

Original languageEnglish
Pages (from-to)550-553
Number of pages4
JournalJournal of Electronic Materials
Issue number5
StatePublished - May 2008


  • GaN
  • HEMT
  • pH sensor


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