In situ investigation of self-induced GaN nanowire nucleation on Si

The nucleation of GaN nanowires grown by molecular beam epitaxy on bare Si(111) and Si(001) has been investigated in situ by reflection high-energy electron diffraction (RHEED) and line-of-sight quadrupole mass spectrometry. On either substrate, the incorporation rate of Ga increases in two steps to steady-state conditions, and the RHEED transmission pattern of GaN appears only in the second stage. Ex situ transmission electron microscopy on samples from both stages grown on Si(001) revealed that the nanowire nucleation is strongly affected by the simultaneous nitridation of the Si substrate.