Electron Paramagnetic Resonance in Semiconductors
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ELECTRON PARAMAGNETIC RESONANCE IN SEMICONDUCTORS
JAMES W. CORBETT, RICHARD L. KLEINHENZ AND NEAL D. WILSEY Institute for the Study of Defects in Solids, Physics Department, State Universitv of New York at Albany, Albany, New York 12222 Naval Research Laboratory, Washington, DC 20375] [* Permanent address:
ABSTRACT The use of electron paramagnetic resonance (EPR) in the study of defects in semiconductors is briefly reviewed, including group IV (C-diamond, Si, Ge, SiC), III-V (A;Sb, GaAs, GaSb, GaP, InAs, InP, InSb), I1-VI (BaO, BaS, BeO, CaO, CaS, CaSe, CdO, CdS, CdSe, CdTe, MgO, SrO, SrS, ZnO, ZnS, ZnSe, ZnTe) and The identification of defects via EPR is described as miscellaneous svstems. Paris the exploitation of that identification as a tool in future studies. ticular attention is paid to Si, where is emerging an integrated panorama of identified defects ranging from point defects to aggregates through intermediate defect configurations (as discussed by Tan) to dislocations and stacking faults; EPR results in Si as a testing ground for the theory of shallow donors, in the understanding of diffusion at high temperatures and in the study of heattreatment defects are discussed as examples of the use of EPR as a tool in defect studies.
INTRODUCTION We have been asked to try to give a perspective view of the use of elecOur space is too limited tron paramagnetic resonance (EPR) in semiconductors. to give details or much depth, but we feel we can give a proper view of the past and future contributions of this field of research. Spectroscopy in general makes contributions to defect studies by the identification of defects and by the use of that identification as a tool in further studies. Characteristically the sharper the spectroscopic lines the more Central to defect identification is the deterincisive the technique can be.
mination of the defect s'rrnmetruj, which mav be manifest by a spectral variation with respect to crystal orientation and which may be probed by the use of polarized light in absorption and in luminescence, by the response to an external field, etc. EPR is simply a form of spectroscopy, specifically Zeeman spectroscopy, except that the usual Zeeman effect involves the splitting of electronic transitions due to a magnetic field; EPR observes the direct transition between the To observe EPR there must be an unpaired spin, Zeeman-split electronic levels. a non-zero paramagnetism, such as may be due to electrons in the conduci.e., tion band [and we will see that conduction electron spin resonance (CESR) has been done in many semiconductors] or a suitably charged point-, line-, or surFor a free electron in space the energy difference between face-defect state. the two Zeeman-split levels of the spin 1/2 system is given by gRH with H- the magnetic field, E- the Bohr magneton and g- a constant determined by the Dirac If that electron is bound to a free atom in space, the theory of the electron. Zeeman levels of the electron may be split and shifted due to various effects such as the hyperfine-interac
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