Magnetoreflectance from GaAs:Mn was measured in the free exciton range for I3 < 5 T and T = 2.0 K. Combining optical results with magnetization data the value for the exchange parameter N0α-Ν0ß = -(2.3f0.6) eV was obtained. Assuming that Ν0 α +0.2 eV, the ferromagnetic p-d exchange interaction was found with the magnitude N0β +2.5 eV.PACS numbers: 78.20.Ls There are two basic issues which bring GaAs:Mn to be an interesting system. The first one is the problem of Mn dopant in III-V compounds, which has been studied for many years but the actual situation is not well understood yet [1][2][3][4][5][6][7]. The mostly accepted model assumes that the neutral Mn acceptor center is formed of Mn3+ core with tightly bound electron and a weakly bound hole (Mn 2+ + hole) [1] (the socalled magnetic acceptor complex (MAC)). This model explains the results of EPR experiments but fails to describe magnetization and susceptibility data [4]. On the other hand, randomly distributed, localized magnetic moments of Mn ions classify GaAs:Mn to the group of the socalled diluted magnetic Semiconduction (DMS) [7]. So far most of the research has been focused on II-VI DMS, whereas results for III-V compounds are very limited.In this communication we report the results of exchange-induced band splitting of bulk GaAs heavily doped with Mn. This study was done by means of the free exciton magnetospectroscopy. Reflectance and the degree of polarization of reflectance in Faraday configuration were measured at T = 2.0 K and magnetic field Β < 5 T for several crystals with different Mn concentration (below 0.1% mole). Additionally magnetization was measured at the same temperature and the field range using a SQUID magnetometer. The Ga 1 -x MnxΑs crystals used in this work were grown by the Czochralski method. Single-phase crystals were obtained only for low Mn concentrations, x < 0.001. We selected three crystals with (951)
The substitution of Ge atoms into ion implanted AlSb is investigated by extended x-ray absorption fine structure spectroscopy. Our results reveal that in the as-implanted material, the implanted Ge atoms are equally distributed between two specific sites, one surrounded by Al atoms and the other surrounded by Sb atoms. After annealing at 750 °C for 5 s, the coordination number of the Ge atoms increases from ∼3 to ∼4 indicating solid phase regrowth of the implantation induced amorphous surface layer. Moreover, in the annealed AlSb, the substitution of Ge atoms into the Al sublattice dominates with an estimated GeAl]:[GeSb]∼0.8:0.2. These results suggest that Ge atoms act preferentially as donor species in AlSb.
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