Arsenic incorporation and its influence on microstructure of wurtzite GaN grown by molecular-beam epitaxy

Abstract

We present a comprehensive study on the incorporation of As in a local area and its influence on the microstructures of wurtzite GaN grown by rf-plasma-assisted molecular-beam epitaxy. Using transmission electron microscopy (TEM) and secondary ion mass spectrometry (SIMS), we found that the incorporation of As in GaN is correlated with the formation of intrinsic basal plane stacking faults. The stacking fault, analyzed by high-resolution TEM, can be regarded as a stacking sequence of cubic GaAs or Ga(N,As) inserted into hexagonal GaN. Indeed, it may be energetically favorable for the As incorporation to form a thin cubic layer in hexagonal GaN, resembling the thermodynamically stable cubic phase for GaAs. We found experimental evidence of As surface segregation and analyzed it by fitting the As SIMS profiles with a one-dimensional empirical surface segregation model. This result declares a significantly large tendency of As surface segregation with the surface segregation coefficient R∼0.99, which indicates the difficulties to incorporate As into GaN, and thus to grow the ternary GaNAs alloys.