## 1 Introduction  
Antimony (Sb)-based high-electron, high-hole mobility III-V binary (InSb, GaSb, AlSb), ternary (InAlSb, InGaSb, GaAlSb), and quaternary (InGaAlSb, InGaPSb, InAlPSb, GaAlPSb, InGaPSb) alloys and heterostructures (quantum wells (QWs) including superlattices (SLs)) have attracted a great deal of attention due to their promises for developing next-generation high-speed infrared opto-electronic and thermo-electric devices [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]. Among others, the indium-based pnictides (InX; X = P, As, and Sb) have recently gained considerable importance. Although the lowest bandgap E\({}_{\rm g}\) (\(\equiv\)0.18 eV) of InSb material is critical for mid-infrared optoelectronics, ultrathin films, QWs, and SLs involving InP (E\({}_{\rm g}\)\(\equiv\) 1.35 eV) and InAs (E\({}_{\rm g}\)\(\equiv\) 0.35 eV) are being used to design metal oxide-semiconductor field-effect transistors (MOSFETs), bipolar junction transistors (BfTs), multi-junction solar cells, light-emitting/receiving devices, infrared detectors (IDs), Shockley diodes (SDs), long-wavelength laser diodes (LDs), photodetectors (PDs), thermoelectric generators (TEGs), etc. [1; 2; 3; 4; 5; 6; 7; 8; 9; 10; 11; 12; 13; 14; 15; 16]. According to [PERSON] et al. [17], several Schottky devices have been integrated recently into different ecosystems for detecting radiation, harmful gases, and pollutants (e.g., ozone O\({}_{3}\), nitrogen oxide NO\({}_{3}\), etc.) and monitoring chemical exposure in the environment. Other devices are also used in satellite communication equipment, high-speed/low-power circuits for bio-medical diagnostics, drug analysis, etc. As compared to the conventional III-V semiconductors, the growth of InP(As)Sb and/or InP(Ga,Al)PSb materials has been and still is quite difficult [18]. As active cladding layers, the exploitation of ultrathin InP\({}_{1-\mathrm{x}}\)Sb\({}_{\mathrm{x}}\) alloy films is considered indispensable for mid-infrared (MIR) laser sources. Due to a large \(\sim\)10.4% lattice mismatch between InP and InP, the growth of defect-free crystalline thin films of InP\({}_{1-\mathrm{x}}\)Sb\({}_{\mathrm{x}}\) ternary alloys is quite challenging. Other issues of preparing Sb-based device structures are linked to the (i) low vapor pressure of Sb, (ii) limitations of the kinetically controlled growth regime, (iii) inexistence of chemically stable hydrides as precursors, and (iv) lack of insulating substrates [16; 17; 18; 19; 20; 21; 22; 23; 24; 25; 26; 27; 28; 29; 30; 31; 32; 33; 34; 35; 36; 37; 38]. Despite these difficulties, several attempts have been made to prepare Sb-based alloys, QWs, and SLs by using liquid-phase epitaxy (LPE), organo-metallic vapor-phase epitaxy (OMVPE), and molecular beam epitaxy (MBE) techniques [39; 40; 41]. There are still a few intrinsic issues that inhibit the design of several important device structures. However, solutions to these problems can be achieved by exploiting appropriate experimental [1; 2; 3; 4; 5; 6; 7; 8; 9; 10; 11; 12; 13; 14; 15; 16; 17] and/or theoretical techniques [18]. Despite many efforts made to grow diverse Sb-based structures, there are limited studies assessing their optical and vibrational characteristics. The experimental methods used for material characterizations include high-resolution X-ray diffraction (HR-XRD) [39; 40], Fourier transform infrared (FTIR) [42; 43; 44], Raman scattering spectroscopy (RSS) [45; 46], photoluminescence (PL) [25; 26; 27; 47], inelastic neutron scattering (INS) [48; 49], inelastic X-ray scattering (IXS) [50], reflection high-energy electron diffraction (RHEED), transmission electron microscopy (TEM) [35; 36; 37; 38], spectroscopic ellipsometry (SE) [28; 29], etc. While HR-XRD [39; 40], FTIR [42; 43; 44], and RSS have played [45; 46] vital roles in appraising the alloy composition x, film thickness d, interfacial structure, and surface relaxation of atoms, their exploitation to assess basic properties of Sb-based ternary and quaternary alloys remained, however, surprisingly enigmatic.