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Room temperature two-dimensional electron gas scattering time, effective mass, and mobility parameters in AlxGa1−xN/GaN heterostructures (0.07 ≤ x ≤ 0.42)

Knight, Sean LU ; Richter, Steffen LU ; Papamichail, Alexis ; Kühne, Philipp ; Armakavicius, Nerijus ; Guo, Shiqi ; Persson, Axel R. ; Stanishev, Vallery ; Rindert, Viktor LU orcid and Persson, Per O.Å. , et al. (2023) In Journal of Applied Physics 134(18).
Abstract

Al x Ga 1 − x N/GaN high-electron-mobility transistor (HEMT) structures are key components in electronic devices operating at gigahertz or higher frequencies. In order to optimize such HEMT structures, understanding their electronic response at high frequencies and room temperature is required. Here, we present a study of the room temperature free charge carrier properties of the two-dimensional electron gas (2DEG) in HEMT structures with varying Al content in the Al x Ga 1 − x N barrier layers between x = 0.07 and x = 0.42 . We discuss and compare 2DEG sheet density, mobility, effective mass, sheet resistance, and scattering times, which are determined by theoretical calculations, contactless Hall effect, capacitance-voltage, Eddy... (More)

Al x Ga 1 − x N/GaN high-electron-mobility transistor (HEMT) structures are key components in electronic devices operating at gigahertz or higher frequencies. In order to optimize such HEMT structures, understanding their electronic response at high frequencies and room temperature is required. Here, we present a study of the room temperature free charge carrier properties of the two-dimensional electron gas (2DEG) in HEMT structures with varying Al content in the Al x Ga 1 − x N barrier layers between x = 0.07 and x = 0.42 . We discuss and compare 2DEG sheet density, mobility, effective mass, sheet resistance, and scattering times, which are determined by theoretical calculations, contactless Hall effect, capacitance-voltage, Eddy current, and cavity-enhanced terahertz optical Hall effect (THz-OHE) measurements using a low-field permanent magnet (0.6 T). From our THz-OHE results, we observe that the measured mobility reduction from x = 0.13 to x = 0.42 is driven by the decrease in 2DEG scattering time, and not the change in effective mass. For x < 0.42 , the 2DEG effective mass is found to be larger than for electrons in bulk GaN, which in turn, contributes to a decrease in the principally achievable mobility. From our theoretical calculations, we find that values close to 0.3 m 0 can be explained by the combined effects of conduction band nonparabolicity, polarons, and hybridization of the electron wavefunction through penetration into the barrier layer.

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type
Contribution to journal
publication status
published
subject
in
Journal of Applied Physics
volume
134
issue
18
article number
185701
publisher
American Institute of Physics (AIP)
external identifiers
  • scopus:85176345317
ISSN
0021-8979
DOI
10.1063/5.0163754
language
English
LU publication?
yes
id
83d17fee-561b-45c4-a193-96b365cab929
date added to LUP
2024-01-02 13:52:15
date last changed
2024-01-02 13:54:41
@article{83d17fee-561b-45c4-a193-96b365cab929,
  abstract     = {{<p>Al x Ga 1 − x N/GaN high-electron-mobility transistor (HEMT) structures are key components in electronic devices operating at gigahertz or higher frequencies. In order to optimize such HEMT structures, understanding their electronic response at high frequencies and room temperature is required. Here, we present a study of the room temperature free charge carrier properties of the two-dimensional electron gas (2DEG) in HEMT structures with varying Al content in the Al x Ga 1 − x N barrier layers between x = 0.07 and x = 0.42 . We discuss and compare 2DEG sheet density, mobility, effective mass, sheet resistance, and scattering times, which are determined by theoretical calculations, contactless Hall effect, capacitance-voltage, Eddy current, and cavity-enhanced terahertz optical Hall effect (THz-OHE) measurements using a low-field permanent magnet (0.6 T). From our THz-OHE results, we observe that the measured mobility reduction from x = 0.13 to x = 0.42 is driven by the decrease in 2DEG scattering time, and not the change in effective mass. For x &lt; 0.42 , the 2DEG effective mass is found to be larger than for electrons in bulk GaN, which in turn, contributes to a decrease in the principally achievable mobility. From our theoretical calculations, we find that values close to 0.3 m 0 can be explained by the combined effects of conduction band nonparabolicity, polarons, and hybridization of the electron wavefunction through penetration into the barrier layer.</p>}},
  author       = {{Knight, Sean and Richter, Steffen and Papamichail, Alexis and Kühne, Philipp and Armakavicius, Nerijus and Guo, Shiqi and Persson, Axel R. and Stanishev, Vallery and Rindert, Viktor and Persson, Per O.Å. and Paskov, Plamen P. and Schubert, Mathias and Darakchieva, Vanya}},
  issn         = {{0021-8979}},
  language     = {{eng}},
  month        = {{11}},
  number       = {{18}},
  publisher    = {{American Institute of Physics (AIP)}},
  series       = {{Journal of Applied Physics}},
  title        = {{Room temperature two-dimensional electron gas scattering time, effective mass, and mobility parameters in Al<sub>x</sub>Ga<sub>1−x</sub>N/GaN heterostructures (0.07 ≤ x ≤ 0.42)}},
  url          = {{http://dx.doi.org/10.1063/5.0163754}},
  doi          = {{10.1063/5.0163754}},
  volume       = {{134}},
  year         = {{2023}},
}