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Keywords:

  • molecular beam epitaxy;
  • nitrides;
  • GaN;
  • Si(111)

Abstract

The mechanism of Si outdiffusion related to the formation of Si-rich GaN clusters during the growth of GaN-on-Si by plasma-assisted molecular beam epitaxy (PAMBE) has been identified. GaN thin films were grown, on high resistivity Si (111) substrates at Ga-rich conditions to favour the 2D step-flow growth mode. Hall-effect measurements revealed very high electron background concentrations, ranging from 2 x 1018 cm-3 to 3 x 1019 cm-3, with degraded carrier mobility in the range of 5-30 cm2/Vs. SEM examination of surfaces and cross-sections of the samples revealed the presence of hollow GaN clusters on the film surface and voids at the Si/III-nitride interface. EDX spot analysis revealed dissolution of Si material in the GaN clusters. Growth of GaN on Si under stoichiometric conditions resulted in films without GaN clusters, which exhibited a serious reduction in carrier concentration, down to 1.4 x 1016 cm-3, with a simultaneous increase of the carrier mobility to 137 cm2/Vs. C-V carrier profile measurements were consistent with Hall-effect measurements and revealed a uniform electron concentration in the GaN film, down to the AlN nucleation layer (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)