Influence of Sb, Bi, Tl, and B on the incorporation of N in GaAs

GaAs:N is an interesting material for many devices due to its unique compositional variation of band gap. Small amounts of N lead to a strong decrease in band gap energy as well as lattice constant. The further addition of In or Sb leads to quaternary alloys with band gap energies below 1.4 eV lattice matched to GaAs. One drawback of these alloys is the low solubility of N in GaAs. Some success has been obtained using low growth temperatures and V/III ratios during organometallic vapor phase epitaxy to kinetically limit phase separation. This article describes mechanisms for N incorporation into the GaAs crystal during growth and shows how surfactants like Sb, Bi, and Tl, as well as B, affect N incorporation. A decrease of the N content in GaAs was found for Sb, Bi, and Tl, which can be explained using a simple Langmuir model with competitive adsorption. The surface morphology of the epitaxial layers and the influence of surfactants was analyzed using atomic force microscopy.