Unexpectedly high energy photoluminescence of highly Si doped GaAs grown by MOVPE

Abstract

Epitaxial GaAs films highly doped with silicon were grown by the MOVPE method in the TMGa-AsH 3-SiH 4-H 2 system. The films were investigated by Hall measurements, photoluminescence (PL) studies and SIMS. A linear relationship between the silane mole fraction in the gas phase and the incorporated Si in the epitaxial films was established by SIMS measurements. The Si concentrations of the samples investigated range from 3×10 18 to 1×10 20 atoms/cm 3, whereas the corresponding Hall concentrations are in the range from 2×10 18 to 5.5×10 18 cm -3. They show a linear increase for the lower Si concentrations and then turn to a decrease for higher Si concentrations. The Hall mobilities decrease with increasing Si mole fraction (2320 to 760 cm 2/V · s, 300 K). The intensities of the near band gap PL are markedly higher and the emission is shifted to higher energies by up to 60 meV as compared to melt- or solution-grown n-GaAs of the same concentration range. It appears that among the different growth techniques the MOVPE process gives highly doped n-type GaAs:Si samples which are more close to perfection.