Neutral manganese acceptor in GaP: An electron-paramagnetic-resonance study

Abstract

In order to clarify the nature of the neutral Mn acceptor in GaP, we have carried out optical-absorption and electron-paramagnetic-resonance ͑EPR͒ experiments using both conventional and thermally detected EPR on semi-insulating GaP:Mn. In thermal equilibrium at low temperatures, all the manganese occurs in the charged acceptor state Mn Ga 2ϩ ͑A Ϫ ͒. By illumination with photon energies greater than 1.2 eV, it can be partially converted into the neutral charge state. The arising photostimulated EPR spectrum shows the characteristic of a tetragonally distorted center with an integer spin. The resonance lines are detectable only at temperatures below 7 K, and their linewidth of about 50 mT is due to the unresolved Mn-hyperfine splitting. We interpret the experimental data in terms of Mn Ga 3ϩ ions on strain-stabilized sites of tetragonal symmetry due to a strong T ⑀ Jahn-Teller coupling within the 5 T 2 ground state. Such a behavior is expected for a 3d 4 defect, as observed for the isoelectronic impurity Cr 2ϩ in GaAs, and other tetrahedrally coordinated semiconductors. The analysis of the EPR spectra thus verifies that, in GaP, the neutral charge state of the Mn acceptor is Mn Ga 3ϩ ͑A 0 ͒ in contrast to its behavior in GaAs and InP. ͓S0163-1829͑96͒06139-5͔

Diluted Magnetic III-V Semiconductors

“…The first one is formed by substitutional manganese Mn3 +Ga , which is in d4 configuration (we denote this center by A0(d4 )). A0(d4 ) was observed in GaP:Mn, in EPR experiment [48]. On the other hand, for GaAs A0(d4 ) centers were not reported.…”

“…Manganese impurity in III-V compounds has been studied for a long time [32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48]. The present understanding of the situation can be summarized as follows: There are essentially three types of Mn centers in III-V compounds.…”

Theoretical Models of Ferromagnetic III‐V Semiconductors

“…For low carrier densities, these valence band holes will be bound to the Mn ion, leading to shallow acceptor levels. This model of carrier-induced ferromagnetism is now fairly well established for (Ga,Mn)As as a result of electron paramagnetic resonance experiments [7], xray magnetic circular dichroism measurements [8,9], and magneto-transport data [10-13].The acceptor impurity levels of Fe and Co [2,3,6,4] are unlikely to lead to high valence band hole concentrations in arsenides or antimonides, as shown in Fig. 1.…”

“…Their model is based on the internal reference rule [6] which states that energy levels derived from the d-shell of the magnetic ion are constant across semiconductor compound families with properly aligned bands. The application of this rule to III-V materials is illustrated in Fig 1 for ionized magnetic impurities substituted on cation sites [2][3][4][5]. The position of the A 2 level for Mn in GaAs, deep in the valence band, suggests that Mn in GaAs is 2+, that its d-shell is occupied by five electrons, and that incorporation of Mn in this and many other (III,Mn)V compounds will result a large density of valence band holes that can mediate ferromagnetic coupling between the S = 5/2 Mn local moments.…”

“…[3]. Acceptor state labeled by A1 and the deep A2 level were obtained from spin-resonance experiments in GaP:Mn [4] and from photoemission in (Ga,Mn)As [5], respectively.…”