Ultrafast pulsed-laser dissociation of Mn-H complexes in GaAs

We demonstrate direct writing of ferromagnetism in hydrogenated Ga _0.96 Mn_0.04 As using femtosecond laser pulses. Tight beam focusing results in the local dissociation of Mn-H defect complexes with sub-500 nm resolution and no detected surface damage. Dot, line, and Hall-bar patterns were drawn in the hydrogenated films by translating the sample during laser irradiation. Magnetotransport measurements on the Hall-bar patterns reveal recovery of hole-mediated ferromagnetism with a Curie temperature of 50 K while magnetic anisotropy is similar to prehydrogenated Ga_0.96 Mn _0.04 As. Interruption of the laser beam during writing leads to the formation of a paramagnetic gap with controllable conductance separating two ferromagnetic line segments. These features, along with the laser tunability of magnetic and electrical properties in the activated regions, represent a planar approach to defining all-semiconductor spintronic structures for device applications.