Physical mechanism of Zn and Te doping process of In0.145Ga0.855As0.108Sb0.892 quaternary alloys

Abstract

We investigated p- and n-type In0.145Ga0.855As0.108Sb0.892 semiconductor alloys grown on GaSb (100) substrates by the liquid phase epitaxy (LPE) technique with different Zinc (Zn) and Tellerium (Te) mole fractions, respectively. Photoluminescence (PL) spectra showed a band gap narrowing effect for p-type doping and a band gap widening for n-type doping, attributed to the type of carrier concentration. The carrier concentration was determined from the band-to-band transition of the PL spectra in the range of 1.20 × 1016 to 2.80 × 1017 and 7.75 × 1016 to 1.02 × 1018 cm−3 for electrons and holes, respectively. Raman spectroscopy measurements showed the phonon modes LO (GaSb–InAs)-like and TO (GaSb–InAs)-like for both types of doping. The frequency dispersion of these modes is closely tied to the presence of native defects, such as vacancies of Ga(VGa), antisites of Ga in Sb (GaSb), and VGa–GaSb complexes. Incorporation of Zn- and Te-doping into the lattice led to a notable reduction in the full width at half maximum (FWHM) of the LO (GaSb–InAs)-like mode, as these dopants effectively diminished native defects. A detailed model is presented for the incorporation of dopants and their effect on the crystal quality. Phonon–plasmon coupling was observed through the L− mode, which overlaps with the TO (GaSb–InAs)-like mode for the carrier concentrations observed in the doped alloys. A theoretical estimation of the frequencies of the coupled modes L+ and L− was implemented as a function of the carrier concentration, based on the effective dielectric function of the quaternary compound. The L+ coupled mode shifts from the phononic to the plasmonic domain for theoretical electron concentrations ranging from ∼1017 to 5 × 1018 cm−3, while in p-type conductivity, the L+ mode remains in the phononic domain for the same range of hole concentrations. The increase in the frequency of the L+ mode with carrier concentration, such as the plasma frequency, provides another reliable method for determining carrier concentrations. This study reveals the physical mechanism of Zn an Te incorporation into InGaAsSb, which is required for the integration of p- and n-type doped quaternary alloys into optoelectronic applications. In addition, it provides a comprehensive understanding of the complex interaction mechanisms, including LO phonon–plasmon coupling modes and optical transitions, opening up new lines for exploring the electrical and structural properties of these materials.