Dynamic grazing incidence fast atom diffraction during molecular beam epitaxial growth of GaAs

Abstract

A Grazing Incidence Fast Atom Diffraction (GIFAD) system has been mounted on a commercial molecular beam epitaxy chamber and used to monitor GaAs growth in real-time. In contrast to the conventionally used Reflection High Energy Electron Diffraction, all the GIFAD diffraction orders oscillate in phase, with the change in intensity related to diffuse scattering at step edges. We show that the scattered intensity integrated over the Laue circle is a robust method to monitor the periodic change in surface roughness during layer-by-layer growth, with oscillation phase and amplitude independent of incidence angle and crystal orientation. When there is a change in surface reconstruction at the start of growth, GIFAD intensity oscillations show that there is a corresponding delay in the onset of layer-by-layer growth. In addition, changes in the relative intensity of different diffraction orders have been observed during growth showing that GIFAD has the potential to provide insight into the preferential adatom attachment sites on the surface reconstruction during growth.

Fast atom diffraction inside a molecular beam epitaxy chamber, a rich combination

“…These have the same period and overall shape as RHEED oscillations carried out under the same conditions. However, unlike RHEED, due to the absence of penetration the phase of these oscillations is exactly the same whatever the diffraction order, whatever the angle of incidence or the crystal direction of the incident beam 8 . This lead us to associate the GI-FAD oscillations to the variations of the surface reflectivity.…”

“…This section is devoted to the behaviour of GIFAD during growth and is based on the recent paper by Atkinson et al 8 . One of the most important uses of RHEED for MBE is the calibration of growth rates during layer-bylayer growth using RHEED intensity oscillations.…”

“…One of the most important uses of RHEED for MBE is the calibration of growth rates during layer-bylayer growth using RHEED intensity oscillations. With GIFAD, these oscillations have been investigated in detail for different projectile energies and angles of incidence as well as azimuthal angle and temperature for GaAs homoepitaxy 8 .…”

“…In this respect it can be metaphorically seen as an AFM operating in the k-space. The MBE chamber is a standard RIBER Compact21 but a splitting flange has been attached to both the source and detector RHEED ports allowing operation of RHEED or GIFAD independently 4,8 . The GIFAD setup is based on a conventional VG EX05 hot filament ion source.…”

“…More recently, a new diffraction technique using the same geometry as RHEED but with keV atoms instead of electrons has emerged as a tool to measure the surface crystalline order on metals 2,3 , semiconductor 4,5 and insulators 6,7 . To test this technique under conventional semiconductor growth conditions, we have attached a GIFAD setup to a conventional III-V MBE chamber 4,8 , and studied the surface reconstructions and dynamics of layer by layer growth for the homoepitaxy of GaAs.…”