Elimination of DX centerlike behavior of donors in heavily doped GaAs

The pressure dependencies of the electrical conductivity, Hall coefficient, and Shubnikov‐de‐Haas effect have been studied for n‐GaAs heavily doped with Sn and Te. The results demonstrate that the energy level related to the DX centers formed by these donors is resonant and degenerate with the conduction band of GaAs. The energy separation of the GaAs conduction‐band minimum and the DX center (E_DX) for the Sn donor has been found to be similar to those of the Si‐ and S‐related DX centers (around 0.3 eV at T≊100 K), whereas E_DX(Te) is much greater, at around 0.55 eV. An analysis of the sample recovery after pressure‐induced freezeout of electrons onto the DX centers has enabled the energy barrier for electron emission from the Sn‐related DX center to the conduction band and the barrier for electron capture by the DX center, the inverse process, to be determined. Both energy barriers are very small compared to those associated with Si‐ and S‐donor‐induced DX centers. The values for E_DX (for Sn and Te) and the barrier sizes (for Sn) measured in this work for donors in GaAs are found to be rather different than the equivalent energies in (Ga,Al)As, and this difference is interpreted as evidence that the local vicinity of the DX center (Ga only or Al/Ga) strongly influences its properties. Finally, these results have led to the proposal of Te as the most effective dopant from the point of view of elimination of the DX centerlike properties of donors in heavily doped GaAs.