Limitations of electrical detection of x-ray absorption fine structure
Abstract
A scheme of capacitance detection for the x-ray absorption fine structure (XAFS) has recently been reported [M. Ishii, Phys. Rev. B 65, 085310 (2002)]. The scheme was intended to expand the applicability of XAFS to study defect centers with deep electronic states within the band gap of a semiconductor. In addition to the proposed measurement of the steady-state capacitance, we introduce the new detection of capacitance transients. The possibilities and limits of the different electrical detection methods are discussed. Special attention is given to the question whether XAFS detected by capacitance can selectively analyze strongly diluted defects. The XAFS at the K edge of gallium and arsenic is measured on GaAs and AlGaAs Schottky diodes containing donor related deep level defects (DX center) and AlGa antisite detects (EL2 center). The oscillation in x-ray absorption is electrically detected by monitoring (i) the photocurrent under short circuit conditions, (ii) the steady-state impedance, and (iii) x-ray-induced capacitance transients. We do not find any significant differences between the electrically and conventionally detected XAFS spectra. From our experimental data and estimates we find no evidence for a site selectivity of capacitance XAFS.
- Publication:
-
Physical Review B
- Pub Date:
- September 2003
- DOI:
- 10.1103/PhysRevB.68.125206
- Bibcode:
- 2003PhRvB..68l5206B
- Keywords:
-
- 61.72.Ji;
- 78.70.Dm;
- 61.10.Ht;
- 71.55.Eq;
- Point defects and defect clusters;
- X-ray absorption spectra;
- X-ray absorption spectroscopy: EXAFS NEXAFS XANES etc.;
- III-V semiconductors