p -type codoping effect in (Ga,Mn)As: Mn lattice location versus magnetic properties

Abstract

In the present work, we perform a systematic investigation on p-type co-doping in (Ga,Mn)As. Through gradually increasing Zn doping concentration, the hole concentration increases, which should theoretically lead to an increase of the Curie temperature (TC) according to the p-d Zener model. Unexpectedly, although the film keeps its epitaxial structure, both TC and the magnetization decrease. The samples present a phase transition from ferromagnetism to paramagnetism upon increasing hole concentration. In the intermediate regime, we observe a signature of antiferromagnetism. By using channeling Rutherford-Backscattering Spectrometry and Particle-Induced X-ray Emission, the substitutional Mn atoms are observed to shift to interstitial sites, while more Zn atoms occupy Ga sites, which explains the observed behavior. This is also consistent with first-principles calculations, showing that the complex of substitutional Zn and interstitial Mn has the lowest formation energy.

The Al Doping Effect on Epitaxial (In,Mn)As Dilute Magnetic Semiconductors Prepared by Ion Implantation and Pulsed Laser Melting

“…Additionally, the thermo-remanent magnetization at 5 K decreases from 23.0, via 20.3, finally to 14.1 emu/cm 3 . Actually, the suppression of magnetization and Curie temperature induced by Al doping has been observed in a series of (Ga,Mn)As samples [ 13 ]; in a study by [ 3 ], there were two different mechanisms proposed: (i) part of Mn atoms are driven into the interstitial sites; and (ii) the localization of carriers is enhanced by Al alloying due to stronger p-d exchange coupling However, in the low Al concentration doped region (<20%), the first function worked dominantly, and a similar phenomenon appeared in Zn-doped (Ga,Mn)As according to our previous research [ 14 ]. This is the most probable explanation for the Al-doped (In,Mn)As case, since, for the highest Al concentration doped sample, it is observed that in addition to the reduction in Curie temperature, the M–T curve deviates from the mean-field approximation, and such a phenomenon is in good agreement with a decrease in substitutional Mn concentration [ 24 ].…”

“…Even for the most canonical DFS (Ga,Mn)As, mostly low-temperature molecular beam epitaxy (LT-MBE) has been employed for its epitaxial film preparation [ 4 , 7 , 8 ], which significantly prohibited the development of DFSs. Moreover, such an obstacle threatens the most conventional technique of semiconductor modification, i.e., co-doping which is productive to present new physics [ 9 , 10 , 11 , 12 , 13 , 14 ]. However, ion implantation followed by the pulsed laser melting method provides an alternative solution to this problem due to its second non-equilibrium grown essence, and therefore, it has been used in several hyper-doping cases in which some are even impossible to approach by LT-MBE [ 15 , 16 , 17 ].…”

Hole compensation effect in III-Mn-V dilute ferromagnetic semiconductors

“…For electrical gating, the samples have to be as thin as several nano-meters due to the extremely high carrier concentrations [2,4,6]. In (Ga,Mn)As co-doped with Be/Zn acceptors, Mn ions are kicked out from substitutional sites to interstitial sites [10,14]. Note that interstitial Mn ions are double donors in GaAs and can develop anti-ferromagnetic coupling [15,16].…”

“…After hydrogenation, a postannealing at low temperature has to be applied to remove the Mn-H complexes and recover the hole concentration over a wide range by varying the annealing time [14]. In (Ga,Mn)As co-doped with Be/Zn acceptors, Mn ions are kicked out from substitutional sites to interstitial sites [11,17]. Note that interstitial Mn ions are double donors in GaAs and can develop anti-ferromagnetic coupling [18,19].…”