IR reflection, attenuated total reflection, and Raman scattering of porous polar III–V semiconductors

Abstract

AbstractOptical properties of porous III–V compounds (GaAs, GaP, InP) in the far infrared (IR) reststrahlen region have been studied by IR reflection and attenuated total reflection (ATR). Comparison of obtained data with Raman scattering (RS) spectra have been performed. Porous layers on III–V compounds wafers were obtained by electrochemical etching. Morphology of porous layers was investigated by methods of atomic force microscopy (AFM) and scanning electron microscopy (SEM), including cross‐section measurements. The ATR measurements allow to study dispersion and damping of surface phonon polaritons (SPPs) in λ = 20–50 µm spectral region. The ATR measurements were carried out in Otto geometry under frequency‐scanning regime at several constant angles of incidence of light. The reflection spectra of porous samples demonstrate change of the reststrahlen band shape due to direct excitation of surface polaritons. It was enabled to excite mixed plasmon–phonon surface modes for semiconductors with free electron concentrations of 1017–1018 cm−3. Frequencies of bulk TO‐, LO‐phonons, surface phonons, and coupled plasmon–phonon modes in the case of high doped semiconductors have been obtained and compared for three spectroscopic methods – reflectance, ATR, and RS.