We have studied the electronic structure of the diluted magnetic semiconductor Ga 1−x Mn x N ͑x = 0.0, 0.02, and 0.042͒ grown on Sn-doped n-type GaN using photoemission and soft x-ray absorption spectroscopy. Mn L-edge x-ray absorption have indicated that the Mn ions are in the tetrahedral crystal field and that their valence is divalent. Upon Mn doping into GaN, new states were found to form within the band gap of GaN, and the Fermi level was shifted downward. Satellite structures in the Mn 2p core level and the Mn 3d partial density of states were analyzed using configuration-interaction calculation on a MnN 4 cluster model. The deduced electronic structure parameters reveal that the p-d exchange coupling in Ga 1−x Mn x N is stronger than that in Ga 1−x Mn x As.

Local structure and effective chemical valency of Mn impurity atoms incorporated in wide-band-gap (Ga,Mn)N epilayers have been investigated by using x-ray absorption fine structure techniques. The x-ray results provide direct evidence for the substitution of majority Mn atoms for the Ga sites in GaN, with an effective valency close to Mn(II), up to a rather high Mn concentration about 2 at. %. A small fraction of the impurity atoms could also form Mn clusters.

The preparation of hexagonal GaN:Mn and GaN:Fe epilayers has been studied by RF-plasma-assisted molecular beam epitaxy. GaN:Fe epilayers exhibit superparamagnetic behavior, presumably due to ferromagnetic inclusions. GaN:Mn epilayers can be expressed in the form of Ga 1−x Mn x N with x up to 0.02, indicating the successful preparation of the GaN-based magnetic alloy semiconductor for the first time. The epilayers are primarily paramagnetic and highly resistive. For epilayers with very high Mn concentration (∼ 10 21 cm −3 ), analysis of the paramagnetic component has revealed the effective spin number S ≈ 2.5 together with the positive paramagnetic Curie temperature. This suggests the presence of ferromagnetic spin exchange between Mn ions.

No abstract

Model calculation and experimental data of circularly-polarized-light-dependent photocurrent in a n-GaAlAs/p-GaInAs/ p-GaAs heterostructure are reported. It is found that, with appropriate heterojunction parameters, spin voltaic effect may survive across the heterojunction and give rise to detectable polarization-dependent photocurrent signals which are greater than those due to the magnetic-circular-dichroism background.