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Longitudinal polar optical phonons in InN/GaN single and double het- erostructures

Ardali, Sukru and Tiras, Engin and Gunes, Mustafa and Balkan, Naci and Ajagunna, Adebowale Olufunso and Iliopoulos, Eleftherios and Georgakilas, Alexandros (2011) 'Longitudinal polar optical phonons in InN/GaN single and double het- erostructures.' physica status solidi (c), 8 (5). pp. 1620-1624. ISSN 1862-6351

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Abstract

Longitudinal optical phonon energy in InN epi-layers has been determined independently from the Raman spectroscopy and temperature dependent Hall mobility measurements. Raman spectroscopy technique can be used to obtain directly the LO energy where LO phonon scattering dominates transport at high temperature. Moreover, the Hall mobility is determined by the scattering of electrons with LO phonons so the data for the temperature dependence of Hall mobility have been used to calculate the effective energy of longitudinal optical phonons.The samples investigated were (i) single heterojunction InN with thicknesses of 1.08, 2.07 and 4.7 μm grown onto a 40 nm GaN buffer and (ii) GaN/InN/AlN double heterojunction samples with InN thicknesses of 0.4, 0.6 and 0.8 μm. Hall Effect measurements were carried out as a function of temperature in the range between T = 1.7 and 275 K at fixed magnetic and electric fields. The Raman spectra were obtained at room temperature. In the experiments, the 532 nm line of a nitrogen laser was used as the excitation source and the light was incident onto the samples along of the growth direction (c-axis). The results, obtained from the two independent techniques suggest the following: (1) LO phonon energies obtained from momentum relaxation experiments are generally slightly higher than those obtained from the Raman spectra. (2) LO phonon energy for the single heterojunctions does not depend on the InN thickness. (3) In double heterostructures, with smaller InN thicknesses and hence with increased strain, LO phonon energy increases by 3% (experimental accuracy is < 1%) when the InN layer thickness increases from 400 to 800 nm

Item Type: Article
Uncontrolled Keywords: optical phonon energy; indium nitrides; mobility; Hall carriers
Subjects: T Technology > TK Electrical engineering. Electronics Nuclear engineering
Divisions: Faculty of Science and Health > Computer Science and Electronic Engineering, School of
Depositing User: Jim Jamieson
Date Deposited: 05 Mar 2012 16:39
Last Modified: 05 Mar 2012 16:39
URI: http://repository.essex.ac.uk/id/eprint/2250

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