Photoluminescence of Zn- and Si-doped GaAs epitaxial layers grown by MOCVD

Low temperature photoluminescence spectroscopy was used to study the band gap shrinkage in Zn and Si doped GaAs films grown by MOCVD technique. The PL experiments were carried out as a function of hole concentration $(10^{17}-1.5x^{20} cm^{-3})$ and electron concentration $(10^{17}-1.5x10^{18} cm^{-3})$. The main peak shifted to lower energy and the full width at half maximum (FWHM) increases with increasing hole concentrations. But in Si doped films the main peak shifted to higher energy and the FWHM increases with increasing electron concentrations. We have obtained an empirical relation for FWHM of PL, \Delta E(p) (eV) = $1.15x10^{-8} p^{1/3} $and for Si doped films \Delta E(n) (ev) = $1.4x10^{-8} n^{1/3}$. We also obtained an empirical relation for the band gap shrinkage, \Delta Eg(eV) = $-2.75x10^{-8} p^{1/3}$ in Zn doped GaAs as a function of hole concentration and \Delta Eg (eV) =$ -1.45x10^{-8} n^{1/3}$ in Si doped GaAs as a function of electron concentration. These values indicates a significant hand gap shrinkage at high doping levels. These relations are considered to provide a useful tool to determine the hole/electron concentration in Zn/Si doped GaAs by low temperature PL measurement, respectively