Temperature dependent effective mass in AlGaN/GaN high electron mobility transistor structures

The temperature-dependence of free-charge carrier mobility, sheet density, and effective mass of a two-dimensional electron gas in a AlGaN/GaN heterostructure deposited on SiC substrate is determined using the THz optical Hall effect in the spectral range from 0.22 to 0.32 THz for temperatures from...

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Bibliographic Details
Published in:Applied physics letters 2012-11, Vol.101 (19)
Main Authors: Hofmann, T., Kühne, P., Schöche, S., Chen, Jr-Tai, Forsberg, U., Janzén, E., Ben Sedrine, N., Herzinger, C. M., Woollam, J. A., Schubert, M., Darakchieva, V.
Format: Article
Language:English
Subjects:
Aluminum gallium nitrides
Carrier density
Density
Electron gas
Gallium nitrides
Heterostructures
Silicon carbide
TECHNOLOGY
TEKNIKVETENSKAP
Two dimensional
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Summary:The temperature-dependence of free-charge carrier mobility, sheet density, and effective mass of a two-dimensional electron gas in a AlGaN/GaN heterostructure deposited on SiC substrate is determined using the THz optical Hall effect in the spectral range from 0.22 to 0.32 THz for temperatures from 1.5 to 300 K. The THz optical Hall-effect measurements are combined with room temperature mid-infrared spectroscopic ellipsometry measurements to determine the layer thickness, phonon mode, and free-charge carrier parameters of the heterostructure constituents. An increase of the electron effective mass from (0.22±0.01)m0 at 1.5 K to (0.36±0.03)m0 at 300 K is observed, which is indicative for a reduction in spatial confinement of the two-dimensional electron gas at room temperature. The temperature-dependence of the mobility and the sheet density is in good agreement with electrical measurements reported in the literature.
ISSN:0003-6951
1077-3118
1077-3118
DOI:10.1063/1.4765351