In situ analysis of Bi terminated GaAs (0 0 1) and Ga(As,Bi) surfaces during growth by MOVPE

Abstract

The influence of trimethylbismuth (TMBi) on the GaAs (001) surface reconstruction is studied in situ by reflection anisotropy spectroscopy (RAS) in a metal organic vapor phase epitaxy (MOVPE) system. During supply of TMBi the RAS spectra indicate a change of the arsenic rich c(4 × 4)β surface reconstruction to a bismuth terminated surface reconstruction. This Bi terminated surface is correlated to the current understanding of growth mechanisms for III/V semiconductors containing small amounts of bismuth. The formation, thermal stability and influence of the ambient conditions on this surface is analyzed. The RAS results are correlated to mass spectrometric studies with a real time fast Fourier transform quadrupole ion trap mass spectrometer (iTrap), which is used inline in the same MOVPE system. Both results indicate an about 40 °C lower decomposition temperature of TMBi compared to TBAs. The decomposition temperatures are determined by mass spectrometry with 290 °C for TMBi and 330 °C for TBAs. Furthermore, the surface reconstruction is studied during growth of Ga(As,Bi) bulk layers grown on GaAs. Under ideal conditions, the RAS measurement of the Ga(As,Bi) growth surface shows the signal of a c(4 × 4)β surface reconstruction which is shifted to lower energies as compared to the GaAs surface reconstruction.