SPring-8, the large synchrotron radiation facility

Inquiry number

SOL-0000000942

Beamline

BL47XU (Micro-CT)

Scientific keywords

A. Sample category	inorganic material
B. Sample category (detail)	semiconductor, magnetic material
C. Technique	photoemission, photoionization
D. Technique (detail)	photoelectron spectra
E. Particular condition	interface
F. Photon energy	X-ray (4-40 keV)
G. Target information	function, electronic state, spin/magnetism

Industrial keywords

level 1---Application area	Semiconductor
level 2---Target	compound semiconductor
level 3---Target (detail)	electric rod
level 4---Obtainable information	electronic state, chemical state
level 5---Technique	XPS

Classification

A40.40 surface・interface chemistry, A80.12 semiconductor, A80.14 magnetic materials, M50.10 photoelectron spectroscopy

Body text

Hole-mediated ferromagnetism has produced reliable estimates of Curie temperature (T_c) for diluted magnetic semiconductors (DMS) such as GaMnAs and predicts that GaMnN will have a T_c above room temperature (RT). However, since doped transition metals introduce deep levels in wide band gap semiconductors like GaN and carriers are localized in these states, it may be difficult to apply the hole-mediated ferromagnetism model to wide band gap GaN-based DMS. Therefore, a different mechanism for magnetism will play a role in GaN-based DMS rather than hole-mediated ferromagnetism. In order to get insight into the mechanism of the magnetism, an electronic structure investigation of GaN-based DMS is necessary. In this research, we have investigated the electronic structure of Cr-doped GaN observed by bulk sensitive hard X-ray photoemission spectroscopy at the excitation energy of 5.95keV. Figure shows the normalized energy distribution curves (EDC’s) of undoped GaN, that of Ga_0.899Cr_0.101N, and the difference spectrum between them, respectively. The Cr-doping does introduce, clearly, new electronic levels in the band gap (C) and causes some change in the valence band structure (A and B). Considering atomic subshell cross section at the excitation energy, the main contribution of the valence band spectra is Ga 4s. The decrease of the intensity in the valence band spectrum by Cr-doping is not only due to the decrease of Ga content but also to the effect of Cr-doping. Namely, the Cr-doping effect on the valence band of GaN and make the in-gap energy state by hybridization between Cr 3d and the second neighbor Ga 4s via the formation of Cr-N bonds. In the Ga 2p core level study, we also observed that the Cr doping influences the second neighbor Ga via the formation of Cr-N bonds. The strong hybridization between Cr 3d and the second neighbor Ga 4s induce the long range interaction between Cr 3d electrons and may an important role in the ferromagnetism of Ga_1-xCr_xN.

The normalized energy distribution curves (EDC’s) of undoped GaN, that of Ga_0.899Cr_0.101N, and the difference spectrum between them, respectively.

[ J.-J. Kim, H. Makino, K. Kobayashi, Y. Takata, T. Yamamoto, T. Hanada, M.-W. Cho, E. Ikenaga, M. Yabashi, D. Miwa, Y. Nishino, K. Tamasaku, T. Ishikawa, S. Shin and T. Yao, Physical Review B 70, 161315(R) (2004), Fig. 1,
©2004 American Physical Society ]

Source of the figure

Original paper/Journal article

Journal title

Phys.Rev.B70, 161315(R)(2004)

Figure No.

Technique

In this research, we have investigated the electronic structure of Cr-doped GaN observed by bulk sensitive hard X-ray photoemission spectroscopy at the excitation energy of 5.95 keV.

Source of the figure

Original paper/Journal article

Journal title

Phys.Rev.B70, 161315(R) (2004)

Figure No.

Required time for experimental setup

１ shift(s)

Instruments

Instrument	Purpose	Performance
Hard X-ray Photoemission Spectroscopy System	Analysis of electronic states in solid and/or interface	Total Energy Resolution: 85meV

References

Related experimental techniques

Questionnaire

The measurement was possible only in SPring-8. Impossible or very difficult in other facilities.
This solution is an application of a main instrument of the beamline.
This solution is application of a new instrument installed in the past two years.

Ease of measurement

Easy

Ease of analysis

Middle

How many shifts were needed for taking whole data in the figure?

Four-nine shifts