Investigation of theDXcenter in heavily dopedn-GaAs

Shubnikov--de Haas and persistent-photoconductivity measurements are used to study the mobility, the free-electron density (n), and the occupancy of the DX center in heavily doped n-GaAs [Si,Sn] as a function of doping level and hydrostatic pressure. The results show that the DX center produces a resonant donor level between the {Γ} and L conduction-band minima at a concentration comparable with the doping level. For the Si-doped samples, comparison with local vibration-mode measurements indicates that the DX level can be identified with SiGa.