First direct observation of EL2-like defect levels in annealed LT-GaAS

N. D. Jäger, A. K. Verma, P. Dreszer, N. Newman, Z. Liliental-Weber, M. van Schilfgaarde, E. R. Weber

Research output: Contribution to journalArticlepeer-review

20 Scopus citations


Nonstoichiometric arsenic-rich GaAs grown at low temperatures by molecular beam epitaxy (LT-GaAs) has been found to be semi-insulating after high-temperature annealing. The origin of this technologically important conversion is not yet fully understood. In order to study this effect, we performed photocurrent measurements on p-LT GaAs-n diodes in the spectral range between 0.75 and 1.5eV at 8K. The photocurrent spectra revealed the following features which are unique to the EL2 level: photoquenching, characteristic photoionization transitions to conduction band minima and a presence of a broad band due to the effect of auto-ionization from the excited state. Moreover, modeling of the optical excitation process using realistic band structure demonstrates that these features cannot be explained by "internal photoemission" originating from As precipitates, as the "buried Schottky barrier model" predicts. This is the first direct experimental evidence for the existence of EL2-like defect levels and their importance for understanding the optical and electronic properties of annealed LT-GaAs.

Original languageEnglish (US)
Pages (from-to)1499-1502
Number of pages4
JournalJournal of Electronic Materials
Issue number12
StatePublished - Dec 1993
Externally publishedYes


  • Defect
  • EL2 defect
  • internal photoemission
  • low-temperature grown GaAs
  • photocurrent
  • photoquenching

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Electrical and Electronic Engineering
  • Materials Chemistry


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