Studies of MBE-Grown Single and Multiple AlN/GaN Heterojunctions

Master's Thesis
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Abstract

The large polarization difference between AlN and GaN provides extremely high electron densities at the interface of AlN/GaN heterojunctions. In this work the growths of high-quality single AlN/GaN heterojunctions with RFMBE are reported, which leads to high-conductivity two-dimensional electron gases. The sheet densities can be tuned from ~5* 1012/cm2 to ~5*1013/cm2 by varying the AlN thickness from 2 - 7 nm. A critical thickness is observed beyond which biaxial strain relaxation and cracking of AlN occurs, and a degradation of carrier mobility is seen to occur at extremely high sheet densities. High-mobility windows are identified with different growth rates. Record low sheet resistances in the range of ~148 å_åü/sq has been achieved. Interface roughness scattering and strain relaxation are identified as the factors preventing lower sheet resistances at present. At low temperature, Shubnikov-de-Haas oscillations have been observed for the first time in single AlN/GaN heterojunctions. The MBE growth for multiple AlN/GaN heterojunctions are also studied. The electron energy states are calculated in the AlN/GaN superlattices which inductivelyto obtain give the miniband structures, for the design of intersubband emitters of detectors. Propagation of longitudinal acoustic phonons through AlN/GaN superlattices is simulated. Finally, phonon filters and phonon cavities are designed for efficient thermal engineering from nitride active layers.

Attributes

Attribute NameValues
URN
  • etd-12182007-152802

Author Yu Cao
Advisor Debdeep Jena
Contributor Greg Snider, Committee Member
Contributor Debdeep Jena, Committee Member
Contributor Huili Xing, Committee Member
Contributor Thosmas Kosel, Committee Member
Degree Level Master's Thesis
Degree Discipline Electrical Engineering
Degree Name MS
Defense Date
  • 2007-12-07

Submission Date 2007-12-18
Country
  • United States of America

Subject
  • MBE

  • Herterojunction

  • AlN

Publisher
  • University of Notre Dame

Language
  • English

Record Visibility and Access Public
Content License
  • All rights reserved

Departments and Units

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