Two-dimensional surface band structure of operating light emitting devices

Shikler, Rafi; Meoded, T.; Fried, N.; Mishori, B.; Rosenwaks, Y.

doi:10.1063/1.370706

Cited by 52 publications

(26 citation statements)

References 15 publications

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“…V CPD values increase from the p-to the n-type sides in accordance with the fact that in our experiment the compensating DC bias that provides V CPD is applied to the tip [17]. This contrast is an evidence of the effective charge separation in the space charge region due to the formation of the junction.…”

Section: Resultssupporting

confidence: 87%

Direct assessment of p–n junctions in single GaN nanowires by Kelvin probe force microscopy

et al. 2016

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Making use of Kelvin probe force microscopy, in dark and under ultraviolet illumination, we study the characteristics of p-n junctions formed along the axis of self-organized GaN nanowires (NWs).We map the contact potential difference of the single NW p-n junctions to locate the space charge region and directly measure the depletion width and the junction voltage. Simulations indicate a shrinkage of the built-in potential for NWs with small diameter due to surface band bending, in qualitative agreement with the measurements. The photovoltage of the NW/substrate contact is studied by analysing the response of NW segments with p-and n-type doping under illumination. Our results show that the shifts of the Fermi levels, and not the changes in surface band bending, are the most important effects under above band-gap illumination. The quantitative electrical information obtained here is important for the use of NW p-n junctions as photovoltaic or rectifying devices at the nanoscale, and is especially relevant since the technique does not require the formation of ohmic contacts to the NW junction.2

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Section: Resultssupporting

confidence: 87%

Direct assessment of p–n junctions in single GaN nanowires by Kelvin probe force microscopy

et al. 2016

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“…a DC voltage is then applied to the tip (or the sample) to nullify the mean vibrational amplitude of the ω frequency. As was described earlier in literature [14][15] this nullifying DC voltage corresponds to the surface potential. This was performed on top of the (right) gold electrode.…”

Section: Kelvin Force Microscopymentioning

confidence: 62%

Morphology of MDMO-PPV:PCBM bulk heterojunction organic solar cells studied by AFM, KFM, and TEM

Martens

Beelen

D’Haen

et al. 2003

Organic Photovoltaics III

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The microstructure of MDMO-PPV:PCBM blends as used in bulk hetero-junction organic solar cells was studied by Atomic Force Microscopy (AFM) and Kelvin Force Microscopy (KFM) to image the surface morphology and by means of Transmission Electron Microscopy (TEM) to reveal images of the film's interior.By introducing KFM, it was possible to demonstrate that phase separated domains have different local electrical properties than the surrounding matrix. Since blend morphology clearly influences global electrical properties and photovoltaic performance, an attempt to control the morphology by means of casting conditions was undertaken. By using AFM, it has been proven that not only the choice of solvent, but also drying conditions dramatically influence the blend structure. Therefore, the possibility of discovering the blend morphology by AFM, KFM and TEM makes them powerful tools for understanding today's organic photovoltaic performances and for screening new sets of materials.

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“…EFM is a noncontact atomic force microscopy ͑AFM͒ technique which uses an oscillating metal-coated tip/cantilever to probe electrical properties of surfaces with better than 100 nm resolution. [6][7][8][9][10][11][12][13][14] Following Ref. 7, the electric force on the tip will in general have electrostatic and capacitive components:…”

Section: Electrostatic Force Microscopymentioning

confidence: 99%

“…In SKPM on operating GaP LEDs for example, an inversion of the surface potential across the p -n junction has been observed due to light absorption in the semiconductor. 11 In this work, we employ a phase-detection EFM method to give a simple, qualitative visualization of voltage drops developing across our heterojunction AlInGaP LEDs. In essence, the oscillating metal tip acts as a passive detector of the voltage drop, which develops across the device layers as the sample is biased.…”

Section: Electrostatic Force Microscopymentioning

confidence: 99%

Evidence for voltage drops at misaligned wafer-bonded interfaces of AlGaInP light-emitting diodes by electrostatic force microscopy

O'Shea

Camras

Wynne

et al. 2001

Journal of Applied Physics

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Electrostatic force microscopy (EFM) with phase detection has been applied to cleaved cross sections of wafer-bonded transparent substrate (TS) AlGaInP light-emitting diode (LED) structures. EFM was performed with the LED under active bias to image the voltage drops across the device layers. Measurements on a nonwafer-bonded, absorbing substrate (AS) AlGaInP LED wafer, showed a voltage drop only at the p–n junction. A TS wafer with high forward voltage (Vf ) showed a much larger voltage drop at the wafer-bonded interface, compared with a normal TS LED wafer. Secondary ion mass spectrometry profiles of these wafers revealed ∼1×1013 cm−2 of carbon at the bonded interface in the high Vf sample, compared to ∼3×1012 cm−2 in the normal wafer. The unwanted voltage drop at the bonded interface was likely caused by a combination of carbon acting as a p-type dopant and the presence of interface states due to a ∼3° in-plane rotational misalignment at wafer bonding.

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Two-dimensional surface band structure of operating light emitting devices

Cited by 52 publications

References 15 publications

Direct assessment of p–n junctions in single GaN nanowires by Kelvin probe force microscopy

Direct assessment of p–n junctions in single GaN nanowires by Kelvin probe force microscopy

Morphology of MDMO-PPV:PCBM bulk heterojunction organic solar cells studied by AFM, KFM, and TEM

Evidence for voltage drops at misaligned wafer-bonded interfaces of AlGaInP light-emitting diodes by electrostatic force microscopy

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