Abstract
We demonstrate x-ray absorption fine structure spectroscopy (XAFS) detected by x-ray beam induced current (XBIC) in single n+-i-n+ doped nanowire devices. Spatial scans with the 65 nm diameter beam show a peak of the XBIC signal in the middle segment of the nanowire. The XBIC and the x-ray fluorescence signals were detected simultaneously as a function of the excitation energy near the Ga K absorption edge at 10.37 keV. The spectra show similar oscillations around the edge, which shows that the XBIC is limited by the primary absorption. Our results reveal the feasibility of the XBIC detection mode for the XAFS investigation in nanostructured devices.
Highlights
X-ray absorption fine structure (XAFS) is an established method for investigating semiconductors, which can give information about the local atomic properties [1,2,3]
The sample was In0.56Ga0.44P single NWs with axial n+-i-n+ doping profiles which were grown via the vapor–liquid–solid method by the use of Au seed particles in a metal organic vapor phase epitaxy system
The NWs were excited with the nanofocused x-ray beam (∼65 nm diameter) at beamline ID-16B at the European synchrotron radiation facility, Grenoble, France (figure 1(a)) [15]
Summary
X-ray absorption fine structure (XAFS) is an established method for investigating semiconductors, which can give information about the local atomic properties [1,2,3]. Fluorescence (XRF), since the measured signal depends on local carrier transport properties in semiconductors. This makes it possible to use x-ray beams as a local probe, similar to electron beam induced current and scanning photocurrent microscopy [8, 9]. The process of generating charge carriers from x-rays starts with an absorption of a primary x-ray photon which excites an inner core electron that results in a core hole and a photoelectron. For the x-ray energy of 10.37 keV and the sample thickness of 180 nm used in this study, we have η = 1867 and pabs = 9.7 × 10−3, for bulk In0.56Ga0.44P This is in contrast to visible light for which only a single electron–hole pair is created per single photon event, η = 1. Conductance measurement, the x-ray photon energy was scanned around the Ga K-edge energy (∼10.37 keV) at the position of the NW where we attained the highest photoconductance signal
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