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Polarization fields in III-nitride nanowire devices
Michael A Mastro1, Blake Simpkins, George T Wang
1US Naval Research Laboratory, Washington, DC 20375, USA. michael.mastro@nrl.navy.mil
Nanotechnology
|March 12, 2010
Summary
Polarization fields are critical for III-nitride nanowire devices. Calculations reveal significant fields at the {0001} facet, leading to p-type transistor operation due to induced carriers.
Area of Science:
- Semiconductor Physics
- Materials Science
- Nanotechnology
Background:
- Polarization fields are crucial for III-nitride thin-film devices.
- III-nitride nanowires are commonly fabricated using the vapor-liquid-solid method, typically resulting in <1120> growth direction.
- These nanowires possess a triangular cross-section with {1101} and {0001} facets.
Purpose of the Study:
- To analyze polarization fields in triangular III-nitride nanowires.
- To investigate the influence of crystal plane orientation on polarization fields.
- To correlate field calculations with experimental device performance.
Main Methods:
- Theoretical analysis of polarization fields in two distinct crystal plane configurations within the nanowire geometry.
- Numerical calculations to determine field strength and sign at different facets.
- Fabrication and characterization of an undoped nanowire transistor.
Main Results:
- Calculations show a significantly larger polarization field at the {0001} facet compared to the {1101} facets.
- The sign of the polarization field is dependent on nanowire orientation and structure.
- An undoped nanowire transistor exhibited p-type behavior attributed to polarization-induced holes at the (0001) AlGaN/GaN interface.
Conclusions:
- Polarization fields play a vital role in III-nitride nanowire device design, comparable to their importance in thin-film devices.
- The {0001} facet experiences substantial polarization fields, influencing carrier behavior.
- Experimental results confirm theoretical predictions, demonstrating polarization-induced p-type conductivity in nanowire transistors.
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