Spatial Mapping of Local Density Variations in Two-dimensional Electron Systems Using Scanning Photoluminescence

Yoon Jang Chung, Kirk W. Baldwin, Kenneth W. West, Nicholas Haug, Johannes Van De Wetering, Mansour Shayegan, Loren N. Pfeiffer

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


We have developed a scanning photoluminescence technique that can directly map out the local two-dimensional electron density with a relative accuracy of ∼2.2 × 10 8 cm -2 . The validity of this approach is confirmed by the observation of the expected density gradient in a high-quality GaAs quantum well sample that was not rotated during the molecular beam epitaxy of its spacer layer. In addition to this global variation in electron density, we observe local density fluctuations across the sample. These random density fluctuations are also seen in samples that were continuously rotated during growth, and we attribute them to residual space charges at the substrate-epitaxy interface. This is corroborated by the fact that the average magnitude of density fluctuations is increased to ∼9 × 10 9 cm -2 from ∼1.2 × 10 9 cm -2 when the buffer layer between the substrate and the quantum well is decreased by a factor of 7. Our data provide direct evidence for local density inhomogeneities even in very high-quality two-dimensional carrier systems.

Original languageEnglish (US)
Pages (from-to)1908-1913
Number of pages6
JournalNano Letters
Issue number3
StatePublished - Mar 13 2019
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • General Chemistry
  • Condensed Matter Physics
  • Mechanical Engineering
  • Bioengineering
  • General Materials Science


  • electron density mapping
  • molecular beam epitaxy
  • photoluminescence
  • quantum well
  • two-dimensional electron system (2DES)


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