A study of the surface structure and composition of annealed Ga0.96Mn0.04As(100)

The surface structure and chemical composition of annealed Ga0.96Mn0.04As(1 0 0) have been studied by scanning tunneling microscopy (STM), auger electron spectroscopy (AES) and low energy electron diffraction (LEED). The samples were As capped and subsequently transferred in-air from the MBE system to the STM chamber. After annealing to 600 K it is found that the Mn segregates to the surface and forms a compound, which is stable up to annealing temperatures of 790 K. For annealing temperatures above 825 K a well-ordered phase exists signified by a LEED pattern consisting of a superposition of a (1 x 6) and a (4 x 2) pattern. LEED and STM measurements demonstrate that the surface is dominated by (1 x 6) domains coexisting with small patches of (4 x 2) domains. By comparing the STM images of the high temperature phase found on Ga0.96Mn0.04As(1 0 0) with the high temperature phases found on ordinary GaAs(1 0 0), we demonstrate differences between annealed Ga0.96Mn0.04As(1 0 0) and GaAs(1 0 0) in both surface morphology and atomic structure. We argue that the Ga0.96Mn0.04As surface is more As rich than the GaAs surface prepared in a similar fashion. Reasons for these differences are discussed.