Diagnostics of semiconductor devices beyond the diffraction limit of light

Hiroaki Fukuda, Toshiharu Saiki, Motoichi Ohtsu

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)


Near-field photocurrent measurements are applied to the diagnostics of the p-n junction of semiconductor devices beyond the diffraction limit of light. In order to probe the internal properties of these devices, modes of propagation into the sample are utilized, retaining high resolution as a result of the contribution of a penetration depth smaller than the aperture diameter of the probe. Near-field photocurrent measurements with multi-wavelength excitation are applied to investigate a lateral p-n junction grown on patterned GaAs(111)A. The slant angle of the p-n junction interface is determined to be 30±8°. The minority carrier diffusion lengths of the electron Ln and the hole Lp of the Si p-n junction are estimated to be 0.47±0.03 and 0.37±0.02 μm, respectively. Near-field photocurrent measurements are also applied to the p-n junction on a Si substrate under the reverse-bias condition in order to estimate the dopant concentration of the p-n junction. The full-width at half maximum (FWHM) of the cross-sectional profile of the near-field photocurrent signal varied upon changing the applied reverse-bias voltage, according to the resulting change in the thickness of the depletion region. From the measured reverse-bias dependence of the FWHM of the cross-sectional profile, the local dopant concentration of the Si substrate was estimated to be 3.5±0.4×1016 cm-3. This result shows good agreement with the dopant concentration (3.1×1016 cm-3) evaluated from the device specifications for device fabrication.

Original languageEnglish
Pages (from-to)445-460
Number of pages16
JournalSensors and Materials
Issue number8
Publication statusPublished - 2001
Externally publishedYes


  • Diffusion length
  • Dopant concentration
  • Fiber probe
  • GaAs device
  • Minority carrier
  • Near-field optical microscope
  • Near-field photocurrent
  • P-n junction
  • Si device

ASJC Scopus subject areas

  • Instrumentation
  • Materials Science(all)


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