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The first two harmonics of a microwave frequency comb (MFC) were measured at a probe which must be within 1 mm of the tunneling junction at the surface of a semiconductor as the sample electrode in a scanning tunneling microscope. The MFC was generated using a passively mode-locked Ti:Sapphire laser with GaN, but lasers with lower photon energy would be required with silicon. The attenuation of the MFC is primarily caused by the spreading resistance in a sub-nm spot at the tunneling junction. Thus, the measured attenuation could be used to determine the carrier density at this spot as an extension of scanning spreading resistance microscopy (SSRM). We anticipate that this effect will enable new nondestructive methods for sub-nm carrier profiling of semiconductors.
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Probing Local Emission Properties in InGaN/GaN Quantum Wells by Scanning Tunneling Luminescence Microscopy
Scanning tunneling electroluminescence (STL) microscopy is performed on a 3 nm‐thick InGaN/GaN quantum well (QW) with [In] = 0.23 such that the main light emission occurs in the green. The technique is used to map the radiative recombination properties at a scale of a few nanometers and correlate the local electroluminescence map with the surface topography simultaneously imaged by scanning tunneling microscopy. While the expected green emission is observed all over the sample, measurements performed on a 500 nm × 500 nm area around a 150 nm‐large and 2.5 nm‐deep hexagonal defect reveal intense emission peaks at higher energies close to the defect edges, features which are not visible in the macrophotoluminescence spectrum of the sample. Via a fitting of the local tunneling electroluminescence spectra, quantitative information on the fluctuations of the intensity, peak energy, width, and phonon replica intensity of the different spectral contributions is obtained, which provides information on carrier localization in the QW. This procedure also indicates that the carrier diffusion length on the probed area of the QW is shorter than 50 nm.
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- Award ID(s):
- 1839077
- PAR ID:
- 10379565
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- physica status solidi (b)
- Volume:
- 260
- Issue:
- 5
- ISSN:
- 0370-1972
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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