Hybridization of Cr $3d–\mathrm{N}$ $2p–\mathrm{Ga}$ $4s$ in the wide band-gap diluted magnetic semiconductor ${\mathrm{Ga}}_{1-x}{\mathrm{Cr}}_x\mathrm{N}$

We observed that Cr doping introduces an electronic state in the band gap in ${\mathrm{Ga}}_{1-x}{\mathrm{Cr}}_x\mathrm{N}$ by using hard x-ray photoemission spectroscopy. Based on first-principles calculations, the electronic state is interpreted to be dominantly Ga $4s$ originated states. The chemical effect of Cr up to the second-nearest-neighbor Ga atoms has also been observed in the core-level spectra of Ga $2p_{3∕2}$. The present results evidence that the Ga valence electrons are strongly affected by the second-nearest-neighbor Cr atoms through Cr $3d\text{−}\mathrm{Ga}$ $4s$ hybridization.

Figure 1

Energy distribution curves (EDC’s) for undoped GaN (open circles) and ${\mathrm{Ga}}_{0.899}{\mathrm{Cr}}_{0.101}\mathrm{N}$ (filled circles) at $\mathrm{h}\nu =5.95\mathrm{keV}$. These EDC’s are obtained by subtracting the trivial background from the experimental spectra. The solid line at the bottom panel shows the difference spectrum.

Figure 2

(a) Calculated total DOS and Cr $3d$ partial DOS based on the DFT with GGA. (b) EDC’s near the VBM of the undoped GaN (open circles) and the ${\mathrm{Ga}}_{1-x}{\mathrm{Cr}}_x\mathrm{N}$ [$x=0.063$ (solid gray circles), 0.101 (solid black circles)]. The intensity of the new energy state in the band gap depends on the Cr concentration. (c) The comparison between the EDC (open circles) of the ${\mathrm{Ga}}_{0.899}{\mathrm{Cr}}_{0.101}\mathrm{N}$ and the quantitatively scaled partial DOS’s both of Cr $3d$ (dotted line) and Ga $4s$ (solid line) in the ${\mathrm{Ga}}_{15}{\mathrm{Cr}}_1{\mathrm{N}}_{16}$ supercell.

Figure 3

The core-level PES’s of (a) N $1s$ and (b) Ga $2p_{3∕2}$ of the undoped GaN (open circles) and the ${\mathrm{Ga}}_{1-x}{\mathrm{Cr}}_x\mathrm{N}$ [$x=0.063$ (solid gray circles), 0.101 (solid black circles)]. The right inset in (b) shows the FWHM variation of the Ga $2p_{3∕2}$ spectra with Cr concentration. The more Cr doped, the broader the FWHM of Ga $2p_{3∕2}$ spectra.