Photoluminescence studies of Si-doped epitaxial GaAs films grown on (100)- and (111)A-oriented GaAs substrates at lowered temperatures

The electrical properties and photoluminescence features of uniformly Si-doped GaAs layers grown on GaAs substrates with the (100) and (111)A crystallographic orientations of the surface are studied. The samples are grown at the same As$_4$ pressure in the growth temperature range from 350 to 510$^{\circ}$C. The samples grown on GaAs(100) substrates possess $n$-type conductivity in the entire growth temperature range, and the samples grown on GaAs(111)A substrates possess $p$-type conductivity in the growth temperature range from 430 to 510$^{\circ}$C. The photoluminescence spectra of the samples exhibit an edge band and an impurity band. The edge photoluminescence band corresponds to the photoluminescence of degenerate GaAs with $n$- and $p$-type conductivity. The impurity photoluminescence band for samples on GaAs(100) substrates in the range 1.30–1.45 eV is attributed to $V_{\mathrm{As}}$ defects and Si$_{\mathrm{As}}$–$V _{\mathrm{As}}$ defect complexes, whose concentration varies with sample growth temperature. Transformation of the impurity photoluminescence spectra of the samples on GaAs(111)A substrates is interpreted as being a result of changes in the $V_{\mathrm{As}}$ and $V_{\mathrm{Ga}}$ defect concentrations under variations in the growth temperature of the samples.