N-face high electron mobility transistors with a GaN-spacer

M. H. Wong, S. Rajan, R. M. Chu, T. Palacios, C. S. Suh, L. S. McCarthy, S. Keller, J. S. Speck, U. K. Mishra

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27 Scopus citations


N-face AlGaN (cap)/GaN (channel)/AlGaN (barrier)/GaN (buffer) high electron mobility transistors (HEMTs) provide a simple solution for strong confinement of the two-dimensional electron gas (2DEG) from the back since carriers are induced on top of the AlGaN barrier. To reduce the adverse effects of random alloy scattering from the AlGaN barrier, an N-face GaN-spacer HEMT was designed with an epistructure consisting of an AlGaN (cap)/GaN (channel)/AlN/GaN (spacer)/AlGaN (barrier)/GaN (buffer). The 2DEG is confined at the GaN (channel)/AlN interface, while the GaN-spacer layer separates the 2DEG from the AlGaN barrier. The large polarization-induced electric field of the AlN and its large conduction band discontinuity with GaN provide strong confinement for good pinch-off and low output conductance under high electric fields. Up to 20% improvement in electron mobility was measured in these devices. The devices showed a current gain cut-off frequency (f t) of 24 GHz and power gain cut-off frequency (f max) of 44 GHz for a nominal gate length of 0.7 μm An output power density of 4.5 W/mm was measured at 4 GHz, with 34% power added efficiency and a gain of 10.3 dB at a drain bias of 40 V.

Original languageEnglish (US)
Pages (from-to)2049-2053
Number of pages5
JournalPhysica Status Solidi (A) Applications and Materials Science
Issue number6
StatePublished - Jun 1 2007

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films
  • Electrical and Electronic Engineering
  • Materials Chemistry


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