Photoemission studies of the annealing-induced modifications of ${\mathrm{Ga}}_{0.95}{\mathrm{Mn}}_{0.05}\mathrm{As}$

Using angle resolved photoemission we have investigated annealing-induced changes in ${\mathrm{Ga}}_{1-x}{\mathrm{Mn}}_x\mathrm{As}$ with $x=0.05$. We find that the position of the Fermi energy is a function of annealing time and temperature. It is also established that the Curie temperature is strongly correlated to the separation between the Fermi level and the valence band maximum. Valence band photoemission shows that the $\mathrm{Mn}3\mathrm{d}$ spectrum is modified by the annealing treatments.

Figure 1

Normal emission core level spectra of $\mathrm{As}3\mathrm{d}$ in ${\mathrm{Ga}}_{0.95}{\mathrm{Mn}}_{0.05}\mathrm{As}$ for different stages in the sequential annealing process. All of the spectra were excited by $81\mathrm{eV}$ photons. The spectra are aligned in energy to show the consistent behavior of the different components.

Figure 2

Fermi level relative $\mathrm{As}3\mathrm{d}$ as a function of annealing temperature. Open symbols representing enforced fitting with rigidly fixed separations between different components and filled symbols free optimum fittings.

Figure 3

Fermi energy and Curie temperature for three samples annealed at different temperatures. The inset shows a section of the hysteresis loop recorded at $5\mathrm{K}$ for the sample with the highest $T_c$.

Figure 4

Normal emission valence band spectra from ${\mathrm{Ga}}_{0.95}{\mathrm{Mn}}_{0.05}\mathrm{As}$ at different stages of annealing. Photon energy $81\mathrm{eV}$.

Figure 5

A simplified model has been fitted to the experimental data for the VB spectra excited by $81\mathrm{eV}$ photons.