Room-temperature ferromagneticlike behavior in Mn-implanted and postannealed InAs layers deposited by molecular beam epitaxy

Abstract

We report on the magnetic and structural properties of Ar- and Mn-implanted InAs epitaxial films grown on GaAs (100) by molecular beam epitaxy and the effect of rapid thermal annealing (RTA) for 30 s at 750 °C. Channeling particle induced x-ray emission (PIXE) experiments reveal that after Mn implantation almost all Mn atoms are substitutional in the In site of the InAs lattice, like in a diluted magnetic semiconductor. All of these samples show diamagnetic behavior. However, after RTA treatment the Mn–InAs films exhibit room-temperature magnetism. According to PIXE measurements the Mn atoms are no longer substitutional. When the same set of experiments was performed with Ar as implantation ion, all of the layers present diamagnetism without exception. This indicates that the appearance of room-temperature ferromagneticlike behavior in the Mn–InAs-RTA layer is not related to lattice disorder produced during implantation but to a Mn reaction produced after a short thermal treatment. X-ray diffraction patterns and Rutherford backscattering measurements evidence the segregation of an oxygen-deficient MnO2 phase (nominally MnO1.94) in the Mn–InAs-RTA epitaxial layers which might be the origin of the room-temperature ferromagneticlike response observed.