High-pressure Raman scattering in InGaN heteroepitaxial layers: Effect of the substrate on the phonon pressure coefficients

R. Oliva, J. Ibáñez, R. Cuscó, A. Dadgar, A. Krost, J. Gandhi, A. Bensaoula, L. Artús
2014 Applied Physics Letters  
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more » ... tering measurements on different In x Ga 1-x N/Si(111) epilayers (0.19 < x < 0.45). We find that the experimental pressure coefficient of the A 1 (LO) mode measured in these samples is larger than that expected from the linear interpolation between the corresponding values of GaN and InN. Similar measurements in InGaN epilayers grown on GaN/sapphire templates yield much lower values, below the linearly interpolated pressure coefficients. We conclude that the phonon pressure coefficients measured in InGaN are mainly determined by the different compressibility of the substrate and epilayer material. Neglecting substrate effects may yield highly inaccurate phonon pressure coefficients and mode Gr€ uneisen parameters. V C 2014 AIP Publishing LLC. [http://dx.
doi:10.1063/1.4870529 fatcat:kcsep5fjfrbwrkxshngzvthyk4