The effects of device dimension, substrate temperature, and gate metallization on the reliability of AlGaN/GaN high electron mobility transistors

F. Ren, S. J. Pearton, Lu Liu, T. S. Kang, E. A. Douglas, C. Y. Chang, C. F. Lo, D. A. Cullen, L. Zhou, David Smith

Research output: Chapter in Book/Report/Conference proceedingConference contribution


The effects of source field plates on AlGaN/GaN High Electron Mobility Transistor reliability under off-state stress conditions were investigated using step-stress cycling. The source field plate enhanced the drain breakdown voltage from 55V to 155V and the critical voltage for off-state gate stress from 40V to 65V, relative to devices without the field plate. Transmission electron microscopy was used to examine the degradation of the gate contacts. The presence of cracking that appeared on both source and drain side of the gate edges was attributed to the inverse piezoelectric effect. In addition, a thin oxide layer was observed between the Ni gate contact and the AlGaN layer, and both Ni and oxygen had diffused into the AlGaN layer. The critical degradation voltage of AlGaN/GaN High Electron Mobility Transistors during off-state electrical stress was determined as a function of Ni/Au gate dimensions (0.1-0.17μm). Devices with different gate length and gate-drain distances were found to exhibit the onset of degradation at different source-drain biases but similar electric field strengths, showing that the degradation mechanism is primarily field-driven. The temperature dependence of sub-threshold drain current versus gate voltage at a constant drain bias voltage were used to determine the trap densities in AlGaN/GaN high electron mobility transistors (HEMTs) before and after the off-state stress. Two different trap densities were obtained for the measurements conducted at 300-493K and 493-573K, respectively.

Original languageEnglish (US)
Title of host publicationCompound Semiconductors for Generating, Emitting and Manipulating Energy
PublisherMaterials Research Society
Number of pages12
ISBN (Print)9781605113739
StatePublished - 2012
Event2011 MRS Fall Meeting - Boston, MA, United States
Duration: Nov 28 2011Dec 2 2011

Publication series

NameMaterials Research Society Symposium Proceedings
ISSN (Print)0272-9172


Other2011 MRS Fall Meeting
Country/TerritoryUnited States
CityBoston, MA

ASJC Scopus subject areas

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


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