No abstract

The authors show a magnetoresistive effect that appears in a lithographically shaped, three-arm nanostructure fabricated from ferromagnetic (Ga,Mn)As layers. The effect, related to a rearrangement of magnetic domain walls between different pairs of arms in the structure, is revealed as a dependence of zero-field resistance on the direction of the previously applied magnetic field. This effect could allow designing devices with unique switching and memory properties.

Electrical properties of lattice-mismatch-induced defects in GaAs/GaAsSb and GaAs/InGaAs heterojunctions have been studied by means of an electron-beam-induced current (EBIC) in a scanning electron microscope and deep-level transient spectroscopy (DLTS). DLTS measurements, carried out with p-n junctions formed at the interfaces, revealed one electron trap and two hole traps induced by the lattice mismatch. The electron trap, at about Ec-0.68 eV, has been attributed to electron states associated with threading dislocations in the ternary compound. By comparing the concentration of this trap, revealed by DLTS, with EBIC results on the diffusion length, obtained for heterojunctions with different lattice mismatches, it is inferred that the minority-carrier lifetime is controlled by dislocations in the epilayer region close to the interface. Two new hole traps have been ascribed to defects associated with the lattice-mismatched interface of the heterostructures.

Two deep electron traps induced by lattice mismatch in relaxed GaAs1−xSbx layers (x=0% to 3%) grown by liquid phase epitaxy (LPE) on GaAs substrates have been revealed by means of deep-level transient spectroscopy. One of the traps, that shows nonstandard, logarithmic capture kinetics and whose energy level is tied to the valence-band edge, has been related to electron states associated with α dislocations. The other trap has been attributed to the EL2 defect and possible reasons of its unexpected formation in the LPE-grown layers are briefly discussed.