Structural and Optical Properties of Porous III-V Semiconductors GaAs, InP Prepared by Electrochemical Etching

ABSTRACT Properties of the electrochemically prepared porous III-V semiconductors, GaAs and InP, have been studied using scanning electron microscopy (SEM), atomic force microscopy (AFM), monochromatic multi-angle-of-incidence (MAI) ellipsometry, Raman scattering (RS), including confocal micro-Raman measurements. Two-layer oxide/porous structures have been observed for porous samples. The optical constants and filling factors of porous layers have been calculated in the frame of the effective medium approximation. The peculiarities of Raman spectra of porous GaAs and InP have been analyzed using the critical point analysis of the phonon dispersion. INTRODUCTION For the last years the researchers actively study different composite materials, in particular porous semiconductors, due to their unusual or unique properties, namely the capability to reduce the optical losses and to increase the efficiency/sensitivity of devices with large specific surface area. Engineering the optical properties of given materials by the modification of their structure is highly motivated due to the perspective possible applications in optoelectronics, quantum electronics, photovoltaics, etc. Besides, the porous semiconductors with rather large specific surface are very useful for sensorics. The porous semiconductor is an appropriate template for a wide variation of effective optical parameters by the incorporation of metal or other semiconductor nanoparticles, and in particular for the design of so-called metamaterials with negative value of the dielectric permittivity or even the refractive index. Therefore determination of porosity of these semiconductors and their effective optical parameters is an important task. In present paper the morphology and optical properties of the porous layers of III-V semiconductors (GaAs and InP) have been studied by atomic force microscopy (AFM) and scanning electron microscopy (SEM), monochromatic multi-angle-of-incidence (MAI) ellipsometry, Raman scattering (RS), including confocal micro-Raman measurements.