Electron mobility in two-dimensional electron gas in AIGaN/GaN heterostructures and in bulk GaN |
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Authors: | M Shur B Gelmont M Asif Khan |
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Affiliation: | (1) Department of Electrical Engineering, University of Virginia, 22903 Charlottesville, VA;(2) APA Optics, APA Inc., 2950 N.E. 84th Lane, 55449 Blaine, MN |
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Abstract: | We report on temperature dependencies of the electron mobility in the two-dimensional electron gas (2DEG) in AIGaN/GaN heterostructures
and in doped bulk GaN. Calculations and experimental data show that the polar optical scattering and ionized impurity scattering
are the two dominant scattering mechanisms in bulk GaN for temperatures between 77 and 500K. In the 2DEG in AIGaN/GaN heterostructures,
the piezoelectric scattering also plays an important role. Even for doped GaN, with a significant concentration of ionized
impurities, a large volume electron concentration in the 2DEG significantly enhances the electron mobility, and the mobility
values close to 1700 cm2/Vs may be obtained in the GaN 2DEG at room temperature. The maximum measured Hall mobility at 80K is nearly 5000 cm2/Vs compared to approximately 1200 cm2/Vs in a bulk GaN layer. With a change in temperature from 300 to 80K, the 2DEG in our samples changes from nondegenerate
and weakly degenerate to degenerate. Therefore, in order to interpret the experimental data, we propose a new interpolation
formula for low field mobility limited by the ionized impurity scattering. This formula is valid for an arbitrary degree of
the electron gas degeneracy. Based on our theory, we show that the mobility enhancement in the 2DEG is related to a much higher
volume electron concentration in the 2DEG, and, hence, to a more effective screening. |
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Keywords: | Gallium nitride Hall factor heterostructure mobility two-dimensional electron gas (2DEG) |
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