Abstract
X-ray photoelectron spectroscopy (XPS) is used to follow some of the electrical properties of a segmented silicon photodetector, fabricated in a p-n-p configuration, during operation under various biasing configurations. Mapping of the binding energy position of Si2p reveals the shift in the position of the junctions with respect to the polarity of the DC bias applied. Use of squared and triangular shaped wave excitations, while recording XPS data, allows tapping different electrical properties of the device under normal operational conditions, as well as after exposing parts of it to harsh physical and chemical treatments. Unique and chemically specific electrical information can be gained with this noninvasive approach which can be useful especially for localized device characterization and failure analyses.
Highlights
The properties of p-n junctions in photodiodes and photovoltaics have been extensively investigated using a combination of electrical and optical analyses tools[13,14,15,16,17,18,19]. All of these powerful techniques provide limited chemical information, if any. Electron spectroscopic techniques, such as Auger electron spectroscopy (AES) and x-ray photoelectron spectroscopy (XPS), in addition to their chemical sensitivity, have the ability to reflect the electrical potential of the medium surrounding the probed atom, since the kinetic energy of the detected electron is effected by such potential[20,21,22,23,24,25,26,27,28,29,30,31,32]
Applications toward investigating devices under more realistic operational conditions are being reported as a consequence of the recent advances in ambient-pressure XPS (APXPS)[43,44,45,46,47]
We previously presented an XPS investigation of a CdS-based photoresistor under working conditions[49], where the electrical potential variations across the device were mapped by recording binding energy positions under an applied +6 V DC bias across the electrodes, and with and without laser illumination at different wavelengths
Summary
The TRW excitation can be utilized to follow the current path(s) through the back contacting of the device at the n-doped segment as schematically shown, while imposing a +3 V DC bias through a small button battery to one of the p-segments Our future work will focus on investigations of charge accumulation and dissipation, and probing photo-excitation effects under flat-band and/or band-bending conditions at or near the junction(s), using both lab-based XPS, as well as synchrotron-based facilities with better lateral and spectral resolution
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