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

Abstract

Optical 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 l ¼ 20-50 mm 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 10 17 -10 18 cm À3. 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.

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

“…The two-layer structure of porous InP contains native oxides and reaction products. We have discussed previously [5] that porous InP layers are much less oxidized by etching than GaAs layers. In common with other studied III-V compounds, the tendency of the formation of pores with lager diameter under the lager current density has been also observed for InP samples (the pore width varying from 1 μm under the treatment conditions j=1 mA/cm 2 , t=5 min to 4 μm under the treatment conditions j=5 mA/cm 2 , t=5 min).…”

Modification of Optical Properties of Porous AIIIBV Layers Produced by Anodic Etching

“…The top layer a few micrometers in thickness consists of native oxides and reaction products. We have discussed previously [15] that porous GaP and InP layers are much less oxidized by the etching than GaAs layers. The bottom layer is porous InP and consists of macrorods.…”

“…The morphology of porous layers depends also on the type and the concentration of an electrolyte, primarily, on its content. Formerly, we have investigated the porous n-type GaAs layers obtained with HF:C 2 H 5 OH:H 2 O electrolyte [10,14,15]. The H 2 SO 4 -based electrolytes were often used for the formation of porous GaP layers by the electrochemical technique at constant high (up to 20 V) external potentials (potentiostatic regime).…”

Infrared reflectance of GaP nanorods

“…The optical studies of por-GaP in the infrared (IR) range have been carried out mainly by the Raman technique (see, e. g., [5][6][7]). The most interesting feature observed was due to Fröhlich modes in the spectral range between transverse optical (TO) and longitudinal optical (LO) excitations and their L-T splitting [5].…”

“…The most interesting feature observed was due to Fröhlich modes in the spectral range between transverse optical (TO) and longitudinal optical (LO) excitations and their L-T splitting [5]. IR reflection was investigated in por-GaP formed in H 2 SO 4 -based [5,6] and HFbased [8] acid electrolytes.…”