Title page for ETD etd-08272007-085537


Type of Document Master's Thesis
Author Willemann, Michael Howard
URN etd-08272007-085537
Title Polymer-Supported Bridges for Multi-Finger AlGaN/GaN Heterojunction Field Effect Transistors (HFETs)
Degree Master of Science
Department Materials Science and Engineering
Advisory Committee
Advisor Name Title
Guido, Louis J. Committee Chair
Aning, Alexander O. Committee Member
Lu, Guo-Quan Committee Member
Keywords
  • Wide-bandgap semiconductor
  • High Electron Mobility Transistor
  • RF power electronics
Date of Defense 2007-08-17
Availability unrestricted
Abstract
Current AlGaN/GaN Heterojunction Field Effect Transistors (HFETs) make use of multiple sources, drains, and gates in parallel to maximize transconductance and effective gain while minimizing the current density through each channel. To connect the sources to a common ground, current practice prescribes the fabrication of air bridges above the gates and drains. This practice has the advantage of a low dielectric constant and low parasitic capacitance, but it is at the expense of manufacturability and robust device operation.

In the study described below, the air bridges in AlGaN/GaN HFETs were replaced by a polymer supported metallization bridge with the intention of improving ease of fabrication and reliability. The DC, high frequency, and power performance for several polymer step heights were investigated. The resultant structures were functional and robust; however, their electrical performance was degraded due to high source resistance. The cause of the high source resistance was found to be thinning of the metallization at the polymer step. The effect was more pronounced for higher step heights.

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