AlGaN channel field effect transistors with graded heterostructure ohmic contacts

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Bajaj S., Akyol F., Krishnamoorthy S., Zhang Y., Rajan S.

APPLIED PHYSICS LETTERS, vol.109, no.13, 2016 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 109 Issue: 13
  • Publication Date: 2016
  • Doi Number: 10.1063/1.4963860
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Yıldız Technical University Affiliated: No


We report on ultra-wide bandgap (UWBG) Al0.75Ga0.25N channel metal-insulator-semiconductor field-effect transistors (MISFETs) with heterostructure engineered low-resistance ohmic contacts. The low intrinsic electron affinity of AlN (0.6 eV) leads to large Schottky barriers at the metal-AlGaN interface, resulting in highly resistive ohmic contacts. In this work, we use a reverse compositional graded n(++) AlGaN contact layer to achieve upward electron affinity grading, leading to a low specific contact resistance (rho(sp)) of 1.9 x 10(-6) x cm(2) to n-Al0.75Ga0.25N channels (bandgap similar to 5.3 eV) with non-alloyed contacts. We also demonstrate UWBG Al0.75Ga0.25N channel MISFET device operation employing the compositional graded n(++) ohmic contact layer and 20 nm atomic layer deposited Al2O3 as the gate-dielectric. Published by AIP Publishing.