Optical investigation of an AlGaN/GaN interface with the presence of a two-dimensional electron gas

Der-Yuh Lin, J. D. Wu, C. C. Hung, C. T. Lu, Y. S. Huang, C. T. Liang, N. C. Chen

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Abstract

In this paper we presented the study of an AlGaN/GaN heterostructure with the presence of a two-dimensional electron gas (2DEG) by using X-ray reciprocal space mapping (RSM), reflectance (R), photoluminescence (PL), electroreflectance (ER) and photoconductivity (PC) measurements. Some important properties such as alloy composition, strain status and layer thickness of AlxGa 1-xN layer and carrier concentration of 2DEG are determined. The structure strain was analyzed by asymmetric RSM. We observed that the AlGaN layer grown on GaN layer was fully strained. The band gap energies of GaN and AlxGa1-xN are identified by PL and R spectrum, from which the Al composition x is determined to be 0.13. Using a semitransparent gate, an external dc bias was applied to control the carrier concentration of 2DEG underneath the AlxGa1-xN layer. We have also performed the ER and PC measurements at various external dc biases. In the ER spectra, not only the energy gap transitions of GaN and AlxGa1-xN but also the 2DEG feature and the FranzKeldysh oscillations (FKOs) were observed. Through the analysis of FKOs, the strength of surface electric field and the 2DEG concentration can be determined. The optical absorption phenomenon in the AlGaN/GaN interface observed by the bias-dependent PC spectroscopy are presented and discussed.

Original languageEnglish
Pages (from-to)125-129
Number of pages5
JournalPhysica E: Low-Dimensional Systems and Nanostructures
Volume43
Issue number1
DOIs
Publication statusPublished - 2010 Nov 1

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All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Atomic and Molecular Physics, and Optics
  • Condensed Matter Physics

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