P.J. Dobson

Dynamics of film growth of GaAs by MBE from Rheed observations

Detailed observations have been made of the intensity oscillations in the specularly reflected and various diffracted beams in the RHEED pattern during MBE growth of GaAs, GaxAl1−xAs and Ge. The results indicate that growth occurs predominantly in a two-dimensional layer-by-layer mode, but there is some roughening, which is enhanced by deviations from stoichiometry and the presence of impurities. In the case of the GaAs (001) −2×4 reconstructed surface a combination of dynamic and static RHEED measurements has provided firm evidence for the presence of one-dimensional disorder features as well as surface steps.

Oscillations in the surface structure of Sn-doped GaAs during growth by MBE

Abstract The presence of predeposited or surface-accumulated Sn during MBE growth modifies the reconstruction of the (001)GaAs surface, as observed by RHEED, at coverages as low as 0.025 monolayer. If growth is initiated on such a surface, oscillation in the intensity modulation of some of the RHEED streaks occurs, with a period equal to the monolayer deposition time of the GaAs. This oscillation decays away at a rate determined by the substrate temperature and Ga flux.

Dynamic RHEED observations of the MBE growth of GaAs

Detailed measurements have been made of the specular beam intensity in RHEED patterns from static and growing GaAs surfaces. The basic parameters investigated were substrate temperature and electron beam azimuth. The results have provided further understanding of growth dynamics and surface disorder, respectively. There is a significant trend away from two-dimensional growth at the higher temperatures, which also correspond to more Ga-rich surface structures. Conversely, surface disorder is apparently greater during growth at the lower temperatures, where the structure is As-rich. The static As-stable 2×4 surface is, however, the most ordered and the most closely two-dimensional. It has also been shown that ordered, two-dimensional growth can be initiated from excess Ga adatom populations.

Effect of arsenic species (As2 OR As4) on the crystallographic and electronic structure of MBE-grown GaAs(001) reconstructed surfaces

Abstract Reaction mechanisms and film properties suggest that the arsenic species (As 2 or As 4 ) have a significant influence on the growth of GaAs films by molecular beam epitaxy. These differences should also be apparent in the surface electronic and crystallographic structures and we have carried out an experimental investigation using reflection electron diffraction, angle-resolved photoemission and surface sensitive core-level photoemission of GaAs(001)-(2 × 4) and -c(4 × 4) reconstructed surfaces prepared using either As 2 or As 4 beams. The (2 × 4) structure is an intrinsic GaAs(001) reconstruction and both electron diffraction and photoemission show that As 2 -grown surfaces are the more highly ordered, although the basic structure is not different. The c(4 × 4) structure is an As-chemisorption induced reconstruction and it is shown from As(3d) core level photoemission in particular that As 2 is much more readily chemisorbed than As 4 on a GaAs surface.