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Chemical Visualization of a GaN p-n junction by XPS.

Caliskan D, Sezen H, Ozbay E, Suzer S - Sci Rep (2015)

Bottom Line: Areal maps of the peak positions under reverse bias are completely decoupled with respect to doped regions and allow a novel chemical visualization of the p-n junction in a 2-D fashion.Other electrical properties of the device, such as leakage current, resistivity of the domains are also tapped via recording line-scan spectra.Application of a triangular voltage excitation enables probing photoresponse of the device.

View Article: PubMed Central - PubMed

Affiliation: Nanotechnology Research Center, Department of Electrical and Electronics Engineering and Department of Physics, Bilkent University, 06800, Ankara, Turkey.

ABSTRACT
We report on an operando XPS investigation of a GaN diode, by recording the Ga2p3/2 peak position under both forward and reverse bias. Areal maps of the peak positions under reverse bias are completely decoupled with respect to doped regions and allow a novel chemical visualization of the p-n junction in a 2-D fashion. Other electrical properties of the device, such as leakage current, resistivity of the domains are also tapped via recording line-scan spectra. Application of a triangular voltage excitation enables probing photoresponse of the device.

No MeSH data available.


Related in: MedlinePlus

XPS line scans.(a) Ga2p3/2 peak recorded across the junction in the line scan mode under +4 Reverse Bias. (b) The equivalent circuit model.
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f5: XPS line scans.(a) Ga2p3/2 peak recorded across the junction in the line scan mode under +4 Reverse Bias. (b) The equivalent circuit model.

Mentions: Further XPS analyses of the junction were carried out by imposing a slow time-varying triangular voltage stimuli of 0–4 V, and also by exposing the sample to light illumination with different colors. In Fig. 4a, the time variations of the Ga2p3/2 peak of a 200 μm spot is shown, where the spot is positioned on the junction covering both the n- and p- sides almost equally. When the device is forward biased, the Ga2p3/2 peaks of the n- and p-regions overlap, but start splitting apart into two components when the device enters the rectifying mode. The splitting increases up to the turning point with a reproducible symmetry. Note, however, the rectification is not all that perfect and small but a measurable slope is also displayed by the p-component, due to unwanted leakage current, which is also present in the I–V characteristics of the device, as shown in the Supplementary Information(SI) section as Figure S1. In addition, as shown in Fig. 4b,c, whereas illumination by green laser does not alter the performance of the p-n junction, the performance is degraded further under violet light illumination, which leads us to postulate the presence of a parallel resistor (Rp) controlled by violet light, i.e. a photoresistor. A simple equivalent circuit can now be formulated, which is given in Fig. 5 and also in the SI section, by assuming the presence of two series resistor in the n- and p- regions and a parallel (photo) resistor across the junction, in order to account for this realistic performance of the device, at least for its d.c. and/or low frequency response11. In principle both the green 532 nm (2.3 eV) and the violet 405 nm light (3.1 eV) should not have contributed to the band to band photoconductivity of GaN with a band-gap of 3.4 eV54. Hence, the presence of deep traps and defects must be causing such changes, which was also reported in our previous studies5657.


Chemical Visualization of a GaN p-n junction by XPS.

Caliskan D, Sezen H, Ozbay E, Suzer S - Sci Rep (2015)

XPS line scans.(a) Ga2p3/2 peak recorded across the junction in the line scan mode under +4 Reverse Bias. (b) The equivalent circuit model.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4566124&req=5

f5: XPS line scans.(a) Ga2p3/2 peak recorded across the junction in the line scan mode under +4 Reverse Bias. (b) The equivalent circuit model.
Mentions: Further XPS analyses of the junction were carried out by imposing a slow time-varying triangular voltage stimuli of 0–4 V, and also by exposing the sample to light illumination with different colors. In Fig. 4a, the time variations of the Ga2p3/2 peak of a 200 μm spot is shown, where the spot is positioned on the junction covering both the n- and p- sides almost equally. When the device is forward biased, the Ga2p3/2 peaks of the n- and p-regions overlap, but start splitting apart into two components when the device enters the rectifying mode. The splitting increases up to the turning point with a reproducible symmetry. Note, however, the rectification is not all that perfect and small but a measurable slope is also displayed by the p-component, due to unwanted leakage current, which is also present in the I–V characteristics of the device, as shown in the Supplementary Information(SI) section as Figure S1. In addition, as shown in Fig. 4b,c, whereas illumination by green laser does not alter the performance of the p-n junction, the performance is degraded further under violet light illumination, which leads us to postulate the presence of a parallel resistor (Rp) controlled by violet light, i.e. a photoresistor. A simple equivalent circuit can now be formulated, which is given in Fig. 5 and also in the SI section, by assuming the presence of two series resistor in the n- and p- regions and a parallel (photo) resistor across the junction, in order to account for this realistic performance of the device, at least for its d.c. and/or low frequency response11. In principle both the green 532 nm (2.3 eV) and the violet 405 nm light (3.1 eV) should not have contributed to the band to band photoconductivity of GaN with a band-gap of 3.4 eV54. Hence, the presence of deep traps and defects must be causing such changes, which was also reported in our previous studies5657.

Bottom Line: Areal maps of the peak positions under reverse bias are completely decoupled with respect to doped regions and allow a novel chemical visualization of the p-n junction in a 2-D fashion.Other electrical properties of the device, such as leakage current, resistivity of the domains are also tapped via recording line-scan spectra.Application of a triangular voltage excitation enables probing photoresponse of the device.

View Article: PubMed Central - PubMed

Affiliation: Nanotechnology Research Center, Department of Electrical and Electronics Engineering and Department of Physics, Bilkent University, 06800, Ankara, Turkey.

ABSTRACT
We report on an operando XPS investigation of a GaN diode, by recording the Ga2p3/2 peak position under both forward and reverse bias. Areal maps of the peak positions under reverse bias are completely decoupled with respect to doped regions and allow a novel chemical visualization of the p-n junction in a 2-D fashion. Other electrical properties of the device, such as leakage current, resistivity of the domains are also tapped via recording line-scan spectra. Application of a triangular voltage excitation enables probing photoresponse of the device.

No MeSH data available.


Related in: MedlinePlus