Phonon–plasmon coupling in Si doped GaN nanowires

Abstract

The vibrational properties of silicon doped GaN nanowires with diameters comprised between 40 and 100 nm are studied by Raman spectroscopy through excitation with two different wavelengths: 532 and 405 nm. Excitation at 532 nm does not allow the observation of the coupled phonon-plasmon upper mode for the intentionally doped samples. Yet, excitation at 405 nm results in the appearance of a narrow peak at frequencies close to that of the uncoupled A 1 (LO) mode for all samples. This behavior points to phonon-plasmon scattering mediated by large phonon wave-vector in these thin and highly doped nanowires.

Wave‐Vector‐Dependent Raman Scattering from Coupled Plasmon–Longitudinal Optical Phonon Modes and Fano Resonance in n‐type Scandium Nitride

“…Coupled plasmon–LO phonon modes of large wave vectors have also been observed in several semiconductors, such as in heavily doped p ‐type C and Ge‐doped GaAs, n ‐type Si‐doped GaN nanowires, n ‐type Al‐doped ZnSe, etc. The large wave‐vector transfer arises from the nonconservation of wave vector due to scattering by ionized impurities and affects the line shapes of the coupled modes, causing a decrease in the frequencies of the LO‐like modes with increasing carrier concentrations . Therefore, along with the knowledge of electronic properties, Raman scattering of the coupled modes can also be effective to determine various carrier scattering mechanism and carrier dynamics studies.…”

“…Coupled plasmon-LO phonon modes of large wave vectors ð q ! Þ have also been observed in several semiconductors, such as in heavily doped p-type C and Ge-doped GaAs, [17,18] n-type Si-doped GaN nanowires, [16] n-type Al-doped ZnSe, [19] etc. The large wave-vector transfer ð q !…”

“…Þ arises from the nonconservation of wave vector due to scattering by ionized impurities and affects the line shapes of the coupled modes, causing a decrease in the frequencies of the LO-like modes with increasing carrier concentrations. [16][17][18][19] Therefore, along with the knowledge of electronic properties, Raman scattering of the coupled modes can also be effective to determine various carrier scattering mechanism and carrier dynamics studies.…”

“…The utility of this technique is particularly important for the determination of the electrical properties of semiconductors as it is not necessary to establish ohmic contacts (which could be difficult to achieve, especially for semiconductor with low carrier concentrations) and since the local resolution of this technique is high compared with the electrical measurements, limited only by the necessity of focusing the laser beam . Similarly, Raman scattering of the coupled mode has also been useful as a nondestructive optical method for the determination of the electronic properties for nanostructured materials, where electrical measurement is extremely challenging to perform, such as on nanowall networks, nanowires, nanoplates, etc.…”