Silicon Donors at the GaAs(110) Surface: A First Principles Study

Abstract

Using the first principles ground state method, we systematically studied the DX center in bulk GaAs and GaAs(110). The DX center is found to be a metastable state in bulk GaAs and completely unstable in the top few layers of GaAs(110). We find that the charge states of SiGa defects on the GaAs(110) surface are localized, and the extra charge is mainly concentrated on the Si atom in the charged system. The localized extra charge of the defect on the surface affects the stability of the GaAs(110) surface. Our results show that the negative charging of SiGa would preferably occur at the surface, whereas the positively charged SiGa defect is unstable at the surface. Finally, our calculated STM images of clean GaAs(110) and charged Si:GaAs(110) using Tersoff–Hamann approximation [Tersoff, J.; Hamann, D. R. Phys. Rev. B1985, 31, 805–813] are in good agreement with experimental results. Our results show that the charge state of defect at the surface has an important influence on the STM image. In addition, we s...