Effect of doping on the magnetic properties of GaMnN: Fermi level engineering

Abstract

GaMnN dilute magnetic semiconductor samples, prepared by metalorganic chemical vapor deposition, are shown to exhibit ferromagnetism or even paramagnetism depending upon the type and concentration of extrinsic impurity present in the film. In addition, GaMnN deposited using growth parameters normally yielding a nonferromagnetic film becomes strongly ferromagnetic with the addition of magnesium, an acceptor dopant. Based upon these observations, it seems that ferromagnetism in this material system depends on the relative position of the Mn energy band and the Fermi level within the GaMnN band gap. Only when the Fermi level closely coincides with the Mn-energy level is ferromagnetism achieved. By actively engineering the Fermi energy to be within or near the Mn energy band, room temperature ferromagnetism is realized.

High Temperature Ferromagnetism and Nano-Scale Phase Separations in Diluted Magnetic Semiconductors and Oxides

“…As important examples we consider (Ga,Mn)N and (Zn,Cr)Te, in which remarkable changes in ferromagnetic characteristics on co-doping with shallow impurities have recently been reported [42,43]. In particular, a strong dependence of saturation magnetization M s at 300 K on co-doping with Si donors and Mg acceptors has been found [42] for (Ga,Mn)N with an average Mn concentration x Mn ≈ 0.2%. Both double exchange and superexchange are inefficient at this low Mn concentration and for the mid-gap Mn level in question.…”

Diluted Ferromagnetic Semiconductors—Theoretical Aspects

“…It is evident that the model in question should apply to a broad class of DMS as well to semiconductors and insulators, in which a constituent, dopant, or defect can exist in different charge states under various growth conditions. As important examples we consider (Ga,Mn)N and (Zn,Cr)Te, in which remarkable changes in ferromagnetic characteristics on codoping with shallow impurities have recently been reported (Reed et al, 2005;Ozaki et al, 2005). In particular, a strong dependence of saturation magnetization M s at 300 K on codoping with Si donors and Mg acceptors has been found (Reed et al, 2005) (Godlewski and Kamińska, 1980) resides about 1 eV above the nitrogen level (Baron, Saminadayar and Magnea, 1998).…”

“…As important examples we consider (Ga,Mn)N and (Zn,Cr)Te, in which remarkable changes in ferromagnetic characteristics on codoping with shallow impurities have recently been reported (Reed et al, 2005;Ozaki et al, 2005). In particular, a strong dependence of saturation magnetization M s at 300 K on codoping with Si donors and Mg acceptors has been found (Reed et al, 2005) (Godlewski and Kamińska, 1980) resides about 1 eV above the nitrogen level (Baron, Saminadayar and Magnea, 1998). Accordingly, for x N ≈ x Cr all Cr atoms become ionized and the Coulomb repulsion precludes the nanocrystal formation.…”

Origin and control of ferromagnetism in dilute magnetic semiconductors and oxides (invited)

“…In particular, a strong dependence of saturation magnetization M s at 300 K on co-doping with Si donors and Mg acceptors has been found for (Ga,Mn)N with an average Mn concentration x Mn ≈ 0.2%. 74 Both double exchange and superexchange are inefficient at this low Mn concentration and for the mid-gap Mn level in question. At the same time, the model of nanocrystal selforganized growth explains readily why M s goes through a maximum when Mn impurities are in the neutral Mn 3+ state, and vanishes if co-doping by the shallow impurities makes all Mn atoms to be electrically charged.…”

“…As important examples we consider (Ga,Mn)N (Ref. 74,75) and (Zn,Cr)Te, 58,76,77 in which remarkable changes in ferromagnetic characteristics on co-doping with shallow impurities have recently been reported. In particular, a strong dependence of saturation magnetization M s at 300 K on co-doping with Si donors and Mg acceptors has been found for (Ga,Mn)N with an average Mn concentration x Mn ≈ 0.2%.…”