Raman-active modes of porous gallium phosphide at high pressures and low temperatures

Abstract

Porous gallium phosphide (GaP) with a honeycomb-like morphology and a skeleton relative volume concentration c = 0.7 was investigated by Raman spectroscopy under pressure up to 10 GPa at T = 5 K. The porous samples were prepared by electrochemical etching. The transverse optical (TO) and longitudinal optical (LO) mode frequencies were found to shift with pressure similarly to those of bulk GaP. As in bulk GaP, the TO feature of the porous GaP exhibits a pressure-induced narrowing which is interpreted in terms of a Fermi resonance. The scattering intensity observed on the low-frequency side of the LO mode is attributed to surface-related Fröhlich mode scattering. The latter results are interpreted on the basis of an effective medium expression for the dielectric function. The Raman spectra indicate that both the morphology and degree of porosity are unaffected by pressure in the range investigated.

Raman scattering of nanoporous semiconductors

“…8. However, two modes were observed and attributed to the F-T and F-L Fröhlich modes in Raman measurements of por-GaP with a honeycomblike morphology under pressure up to 10 GPa and at T D 5 K. 92 A surface-related phonon mode in porous GaP at 397 cm 1 was first observed by Tiginyanu et al 93 and interpreted in terms of a Fröhlich mode on the basis of an effective medium approach. 94 It was shown that its wavenumber decreases with increasing anodization current.…”

Phonon polariton modes in porous III–V semiconductors

“…Some of the areas of current interest are (i) photonic polaritonic materials [5], (ii) left handed materials [6], (iii) porous semiconductor materials [7,8], (iv) microcavity polaritons [9], and (v) those associated with acoustic modes in a piezoelectric material [10,11]. Some of these phenomena are made use of in devices for supporting spontaneous emission, for projecting light along a specific path in novel laser geometry and in efficient frequency conversion [12][13][14] and so on.…”

“…However, the studies on Qwire and QDOT systems are sparse [18,19]. After the path breaking work of Canham [20], several authors have studied the optical properties of the porous semiconducting materials [7,8]. Raman spectroscopy has proved to be the most successful technique for such studies.…”

“…Raman spectroscopy has proved to be the most successful technique for such studies. Effect of hydrostatic pressure on the Raman shifts in porous GaP and on a few other III-V porous semiconductors are available [7].…”

“…In Raman scattering experiments [7] the wavelength of light used is much larger than the average structural dimensions. Also in the case of IR reflectance measurements, the wavelength is much larger than the sample dimensions.…”