Characterization of Zn-Doped Ga_0.86In_0.14As_0.13Sb_0.87

Controlled doping of quaternary alloys of Ga_0.86In_0.14As_0.13Sb_0.87 with zinc is fundamental to obtain the p-type layers needed for the development of optoelectronic devices based on p–n heterojunctions. GaInAsSb epitaxial layers were grown by liquid phase epitaxy, and Zn doping was obtained by incorporating small Zn pellets in the growth melt. The chemical composition was obtained by X-ray dispersive energy microanalysis (EDX). The chemical composition homogeneity of the films was demonstrated by Raman scattering. Low-temperature photoluminescence (LT-PL) spectroscopy was used to study the influence of the Zn acceptor levels on optical properties of the epilayers. For the undoped sample, the LT-PL spectrum showed a narrow exciton-related peak centered at around 648 meV with a full width at half maximum (FWHM) of about 7 meV, which is evidence of the good crystalline quality of the layers. For higher Zn-doping, the LT-PL spectra show the presence of band-to-band and donor-to-acceptor transitions, which overlap as the Zn concentration increases. The band-to-band radiative transition (E_M) shifts to lower energies as Zn doping increases due to a band-filling effect as the Fermi level enters into the valence band, which might be used to estimate the hole concentration in the grown samples.