Influence of Annealing on Mn Implanted GaAs Films

Magnetic semiconductors with high Curie temperatures are very promising materials for spintronic applications. An approach to fabricate GaMnAs is the Mn-implantation of GaAs followed by pulsed laser annealing (PLA) [1,2]. We investigated the influence of the Mn concentration and PLA conditions, e.g. number of laser pulses, on the structural and magnetic properties of (001)-oriented GaMnAs. Results from heatflow calculations helped us to understand the PLA process. Using SQUID magnetometry, we reveal a strong decrease of the saturation magnetization with increasing number of laser pulses. Zero field cooled/ field cooled measurements were performed to investigate the magnetization of the annealed GaMnAs layer. We found a spontaneous magnetization below the Tc and a large out-of- plane anisotropy. HR-XRD measurements revealed a lattice expansion normal to the surface after implantation. In dependence on the number of pulses, PLA decreases the strain (1 pulse) or overcompensates the strain (10 and 100 pulses). We conclude that Mn-implantation into GaAs followed by 1 laser pulse allows for the fabrication of strongly anisotropic, diluted magnetic GaMnAs. The drawback of the Mn-implantation is the loss of As from the GaAs surface as detected by means of Auger electron spectroscopy. Co-implantation with suitable elements is a possible approach to countervail the magnetic properties of annealed GaMnAs.

[1] M. A. Scarpulla, O. D. Dubon, K. M. Yu, O. Monteiro, M. R. Pillai, M. J. Aziz, and
M. C. Ridgway, Appl. Phys. Lett. 82, 1251 (2003).

[2] M. A. Scarpulla, R. Farshchi, P. R. Stone, R. V. Chopdekar, K. M. Yu, Y. Suzuki, and
O. D. Dubon, J. Appl. Phys. 103, 073913 (2008).