Effect of Si doping on the dislocation structure of GaN grown on the A-face of sapphire

  • Ruvimov S
  • Liliental-Weber Z
  • Suski T
 et al. 
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Abstract

Transmission electron microscopy, x‐ray diffraction, low‐temperature photoluminescence, and Raman spectroscopy were applied to study stress relaxation and the dislocation structure in a Si‐doped GaN layer in comparison with an undoped layer grown under the same conditions by metalorganic vapor phase epitaxy on (11.0) Al2O3. Doping of the GaN by Si to a concentration of 3×1018 cm−3 was found to improve the layer quality. It decreases dislocation density from 5×109 (undoped layer) to 7×108 cm−2 and changes the dislocation arrangement toward a more random distribution. Both samples were shown to be under biaxial compressive stress which was slightly higher in the undoped layer. The stress results in a blue shift of the emission energy and E 2 phonon peaks in the photoluminescence and Raman spectra. Thermal stress was partly relaxed by bending of threading dislocations into the basal plane. This leads to the formation of a three‐dimensional dislocation network and a strain gradient along the c axis of the layer.

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Authors

  • Joel AgerLawrence Berkeley National Laboratory

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  • Sergei Ruvimov

  • Zuzanna Liliental-Weber

  • Tadeusz Suski

  • Jack Washburn

  • Joachim Krueger

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