Nonlinear Optical Characterization of GaN Layers Grown by MOCVD on Sapphire

Abstract

Optical second and third harmonic generation measurements were carried out on GaN layers grown by metalorganic chemical vapor deposition (MOCVD) on sapphire substrates. The measured d 33 is 33 times the d 11 of quartz. The angular dependence of second-harmonic intensity as well as the measured ratios d 33 /d 15 = -2.02 and d 33 /d 31 = -2.03 confirm the wurzite structure of the studied GaN layers with the optical c-axis oriented perpendicular to the sample surface. Fine oscillations were observed in the measured second and third harmonic angular dependencies. A simple model based on the interference of the fundamental beam in the sample was used to explain these oscillations.

Temperature dependence of Raman scattering in porous gallium phosphide

“…The observation of two RS peaks F1 and F2 at low temperatures (figure 4) may be attributed to the longitudinal-transverse (L-T) splitting of the Fröhlich mode [22]. One can note that the L-T splitting of a Fröhlich mode was observed recently [41,42] in porous structures of SiC, GaP and InP compounds by Fourier transform infrared spectroscopy.…”

“…Fröhlich-type surface related vibrations were observed in porous structures of different III-V compounds [11,14,[20][21][22]. In porous GaP, for instance, the Fröhlich mode frequency was found to depend upon the degree of porosity and dielectric function of the surrounding medium [14,[21][22][23].…”

“…Fröhlich-type surface related vibrations were observed in porous structures of different III-V compounds [11,14,[20][21][22]. In porous GaP, for instance, the Fröhlich mode frequency was found to depend upon the degree of porosity and dielectric function of the surrounding medium [14,[21][22][23]. Under hydrostatic pressure, an increase in the frequency gap between the Fröhlich mode and the LO phonon was observed and attributed to pressure-induced changes in the anharmonicity of the Fröhlich vibrations [24].…”

Fröhlich modes in porous III-V semiconductors

“…Porous GaP (por-GaP) layers and free-standing membranes proved to be excellent materials to use to study the peculiarities inherent to porous III-V semiconductor compounds. Recent progress in the fabrication of por-GaP by electrochemical etching allows one to control and to reproduce properties of the porous structures such as the morphology and basic electrical parameters in a desired way [11][12][13][14]. An enhanced optical response, new radiation and scattering properties and Fröhlich modes have already been reported for several porous III-V semiconductors [15][16][17][18][19][20][21].…”