Excitonic giant Zeeman effect inGaN:Mn3+

Abstract

We describe a direct observation of the excitonic giant Zeeman splitting in Ga1-xMnxN, a widegap III-V diluted magnetic semiconductor. Reflectivity and absorption spectra measured at low temperatures display the A and B excitons, with a shift under magnetic field due to s,p-d exchange interactions. Using an excitonic model, we determine the difference of exchange integrals between Mn 3+ and free carriers in GaN, N0(α − β) = −1.2 ± 0.2 eV. Assuming a reasonable value of α, this implies a positive sign of β which corresponds to a rarely observed ferromagnetic interaction between the magnetic ions and the holes.PACS numbers: 75.50. Pp, 75.30.Hx, 78.20.Ls, 71.35.Ji Diluted magnetic semiconductors (DMS) of the III-V type, such as (Ga,Mn)As, attract attention mainly because of their magnetic and electron transport properties. The direct measurement of the strength of the ion-carrier coupling, as routinely performed in II-VI DMS, through the observation of the giant Zeeman splitting of excitons, was not accessible for III-V DMS due to free carriers introduced by magnetic ions. Hence conclusions have been based on studies of extremely diluted samples 1 or on a complex interpretation of experimental data. 2,3,4Here we show and quantitatively describe excitons in GaN, with a shift due to the s,p-d coupling to Mn ions incorporated as neutral centers (Mn 3+ ). We present both the magneto-optical study of specially designed and thoroughly characterized Ga 1−x Mn x N layers, and the excitonic model needed to determine the strength of ioncarrier coupling. Such a model is needed, because excitonic effects are especially strong in wide-gap semiconductors. Hence the giant Zeeman effect measured on the excitons cannot be identified with that of band-to-band transitions, as it has been done for other wurtzite DMS. 5

Fe dopant in ZnO: 2+ versus 3+ valency and ion-carrier s,p−d exchange interaction

“…The obtained N 0 β, 0.5−1 eV, is smaller than typical ironhole exchange integrals for II-VI compounds, [75][76][77][78] but of the same order as effective exchange integrals reported for wide gap DMSs 8,9,[79][80][81][82][83] With the increasing U (Fe), t 2↑ approaches the valence band (see Fig. 2), which increases the spin splitting of the VBM, and for the U (Fe)= 4 eV the N 0 β reaches 2.0 eV .…”

Upper bound for thes−dexchange integral inn-(Ga,Mn)N:Si from magnetotransport studies

“…In the case of magnetically doped wurtzite (wz) GaN, exciton magnetospectroscopy [25][26][27] and magnetic circular dichroism [28] were employed to evaluate the sp-d exchange energies in films deposited by metal-organic vapor phase epitaxy (MOVPE). These methods provide the magnitude of N 0 (β − α) rather accurately.…”

Excitonic Giant Zeeman Effect in Wide Gap Diluted Magnetic Semiconductors Based on ZnO and GaN

“…[5] for ZnO:Co 2+ and will be given in Ref. [7] for GaN:Mn 3+ . For (Ga,Mn)N, we use the band parameters given in Ref.…”