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Type of Document Master's Thesis Author Deen, David Aaron Author's Email Address ddeen@nd.edu URN etd-04262007-153718 Title Fabrication of Ultra-Shallow Channel AlN/GaN High Electron Mobility Transistors Degree Master of Science in Electrical Engineering Department Electrical Engineering Advisory Committee
Advisor Name Title Huili (Grace) Xing Committee Chair Alan Seabaugh Committee Member Debdeep Jena Committee Member Keywords
- MBE
- transconductance
- GaN
- AlN
- HEMT
- MISFET
- heterostructure
- nitride
Date of Defense 2007-04-18 Availability restricted Abstract We present the first working AlN/GaN HEMT with a 3 nm AlN barrier layer that provides high polarization induced charge densities for the 2DEG. Without the need for impurity doping themobility of the AlN/GaN heterostructure is drastically increased and is the basis of HEMT technology. Also enhanced by the lack of alloy
disorder scattering at the interface, the AlN/GaN heterostructure appears to be the ideal candidate for high speed applications. As the AlN barrier is quite thin it is presupposed that a high leakage current will persist through the gate contact. High-K dielectrics offer a possible solution to reduced gate leakage and allow the
transconductance and scaling of the device to be optimized.
Preliminary results on non-optimized AlN/GaN devices show decent current-voltage characteristics amongst other characterization measurements performed. A major issue arose with
obtaining ohmic contact to high quality AlN/GaN heterostructures. Lower quality AlN barriers have large dislocation densities and are easy to form ohmic contacts on, however with higher crystalline
quality AlN, conventional methods of forming ohmic contacts seem to be of little value. Conventional and unconventional ohmic contact
experiments to high quality AlN have been performed and discussed.
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