Self-assembled In1−xMnxAs quantum dots (0.19⩽x⩽0.45) have been grown on GaAs (100) substrates by low-temperature molecular beam epitaxy. The microstructure analysis revealed that the uniformly distributed In1−xMnxAs dots have a zinc blende structure as x⩽0.38. Furthermore, all samples exhibit ferromagnetic state at 5K, and their Curie temperatures range from 260to340K varying with x. These (In, Mn)As quantum dots are promising for room-temperature spintronic devices.

Articles you may be interested inOrigin of ferromagnetism in self-assembled Ga 1 − x Mn x As quantum dots grown on Si Appl. Phys. Lett. 97, 242505 (2010); 10.1063/1.3526378 Room-temperature ferromagnetism in self-assembled (In, Mn)As quantum dots Appl. Phys. Lett. 90, 022505 (2007); 10.1063/1.2430930 Formation and property of InSb self-assembled quantum dots on GaAsSb lattice matched to InPSelf-assembled In 0.79 Mn 0.21 As quantum dots were successfully grown on GaAs ͑001͒ substrates by low-temperature molecular beam epitaxy. Atomic force microscopy and high-resolution transmission electron microscopy confirm the formation of quantum dots. High-resolution lattice image suggests that In 0.79 Mn 0.21 As dots are single phase with zinc-blend structure. The dots exhibit typical ferromagnetic state at 5 K and demonstrate a Curie temperature of ϳ290 K which is much higher than those of ͑In, Mn͒As diluted magnetic semiconductor alloys ever reported. The significant increase in Curie temperature can be attributed to the much higher Mn content in the dots, and the possible enhancement of the hybridization strength between the quantum-confined holes in the dots and the itinerant holes in the semiconductor valence band.

An atomically flat and uniform reaction layer of Mn(Ga)As was found to self-organize at the (Ga,Mn)As∕IrMn interface by postannealing. The Mn(Ga)As layer exhibits strong ferromagnetic characteristics up to the measured 300K. In particular, the manifested horizontal shift of field-cooled hysteresis loops shows a clear signature of exchange bias attributable to the exchange coupling between IrMn and Mn(Ga)As. Implication from composition analyses, exchange-bias effect, and thickness dependence of the Mn(Ga)As layer versus annealing conditions is also discussed.

Arsenic precipitation in ''superlattice'' structures of alternately undoped and ½Si ¼ 3 Â 10 18 cm À3 -doped GaAs grown at 250 C on (100), (311)A, and (311)B GaAs substrates has been studied using transmission electron microscopy. It is found that upon postgrowth annealing at 800 C, As precipitates are nearly confined in the Si-doped regions, forming two-dimensional cluster arrays located approximately at the center of each Si-doped layer. The results also show that the As precipitates in the (311)B substrate are slightly denser and larger than those in the (311)A substrate and both are markedly denser and larger than those in the (100) substrate. This can be attributed to the varying excess arsenic incorporations in differently orientated substrates.