'Kink' in AlGaN/GaN-HEMTs: Floating buffer model

Manikant Singh*, Michael Uren, Trevor Martin, Serge Karboyan, Hareesh Chandrasekar, Martin Kuball

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

41 Citations (Scopus)
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We report on a floating buffer model to explain 'kink,' a hysteresis in the output characteristics of Fe-doped AlGaN/GaN HEMTs observed at low drain bias. Unintentionally doped background carbon can make the GaN buffer p-type allowing it to electrically float. We further note that reverse bias trap-assisted leakage across the junction between the 2DEG and the p-type buffer can provide a mechanism for hole injection and buffer discharging at just a few volts above the knee, explaining the 'kink' bias dependence and hysteresis. We show that HEMTs with a different background carbon have dramatically different kink behaviors consistent with the model. Positive and negative magnitude drain current transient signals with 0.9-eV activation energy are seen, corresponding to changes in the occupation of carbon acceptors located in different regions of the GaN buffer. The observation of such signals from a single trap calls into question conventional interpretations of these transients based on the bulk 1-D deep-level transient spectroscopy (DLTS) models for GaN devices with floating regions.

Original languageEnglish
Article number8432505
Pages (from-to)3746-3753
Number of pages8
JournalIEEE Transactions on Electron Devices
Issue number9
Early online date10 Aug 2018
Publication statusPublished - 1 Sept 2018

Structured keywords

  • CDTR


  • Carbon doping
  • drain current transient spectroscopy
  • floating buffer
  • GaN
  • HEMT
  • iron doping
  • kink effect
  • traps


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