Distributed surface donor states and the two-dimensional electron gas at AlGaN/GaN heterojunctions

Luke Gordon, Mao Sheng Miao, Srabanti Chowdhury, Masataka Higashiwaki, Umesh K. Mishra, Chris G. Van De Walle

Research output: Contribution to journalArticlepeer-review

60 Scopus citations


Surface donor states with distributed and finite density are implemented in Schrödinger-Poisson simulations of AlGaN/GaN high electron mobility transistors, with the goal of studying their effects on the two-dimensional electron gas. Our recent experimental observations of an increasing surface barrier height with increasing AlGaN thickness are fitted very well by simulations including surface donor levels represented by a constant density of states (DOS) with a density on the order of 1013 cm-2 eV-1. The highest occupied surface states are found to be around 1 eV below the conduction-band minimum, considerably higher in energy than previously reported single surface donor levels. These trends can be explained by the features of oxidized AlGaN surfaces. Furthermore, the surface DOS that fit the experimental results are found to be larger for samples with higher Al concentration.

Original languageEnglish (US)
Article number505501
JournalJournal of Physics D: Applied Physics
Issue number50
StatePublished - Dec 22 2010

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Acoustics and Ultrasonics
  • Surfaces, Coatings and Films


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