Understanding the origin of mobility enhancement in wedge-shaped c-GaN nanowall networks utilizing spectroscopic techniques

Recently, the electron mobility in wedge-shaped c-GaN nanowall networks has been estimated to cross the theoretical mobility limit for bulk GaN. Significant blue-shift of the bandgap has also been observed. Both the findings are explained in terms of two-dimensional electron gas (2DEG) formed at the...

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Veröffentlicht in:Journal of applied physics 2022-11, Vol.132 (19)
Hauptverfasser: Kaur, Amandeep, Bera, Kousik, Yadav, Santosh Kumar, Shivaprasad, S. M., Roy, Anushree, Dhar, Subhabrata
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container_issue 19
container_start_page
container_title Journal of applied physics
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creator Kaur, Amandeep
Bera, Kousik
Yadav, Santosh Kumar
Shivaprasad, S. M.
Roy, Anushree
Dhar, Subhabrata
description Recently, the electron mobility in wedge-shaped c-GaN nanowall networks has been estimated to cross the theoretical mobility limit for bulk GaN. Significant blue-shift of the bandgap has also been observed. Both the findings are explained in terms of two-dimensional electron gas (2DEG) formed at the central vertical plane of the walls due to the polarization charges at the two inclined faces. Carrier concentration and mobility have earlier been determined from thermoelectric power and conductivity measurements with the help of a statistical model. Due to the network nature of the system, direct measurements of these quantities from Hall experiments are not possible. Search for a better way to estimate mobility in this system thus becomes important. Since, strain can also lead to the blue-shift of the bandgap, it is also imperative to evaluate carefully the role of strain. Here, using Raman spectroscopy, we have estimated carrier concentration and mobility in these nanowall networks with varied average tip-widths. Depth distribution of strain and luminescence characteristics are also studied. The study reveals that strain has no role in the bandgap enhancement. Moreover, the electron mobility, which is determined from the lineshape analysis of the A1(LO)-plasmon coupled mode in Raman spectra, has been found to be significantly higher than the theoretical limit of mobility for bulk GaN for the same electron concentration. These results thus corroborate the picture of polarization induced vertical 2DEG formation in these walls as predicted theoretically.
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source AIP Journals Complete; Alma/SFX Local Collection
subjects Blue shift
Carrier density
Coupled modes
Electron gas
Electron mobility
Energy gap
Networks
Raman spectra
Raman spectroscopy
Spectrum analysis
Statistical models
Vertical polarization
title Understanding the origin of mobility enhancement in wedge-shaped c-GaN nanowall networks utilizing spectroscopic techniques
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