SIMULATION OF MOLECULAR BEAM

HOMOEPITAXIAL GROWTH OF GAAS

RESULTS

An analysis of the surface patterns can be done by looking at the radial distribution function (RDF) of the adatoms on the GaAs surface. Fig.1 and Fig.2 show the RDFs for different coverage ratios.
 
 

(Fig. 1) The graphs show the RDF and a typical surface configuration of the adatoms on the GaAs surface. The coverage ratio is 60% of a full layer of GaAs. The simulation temperatures were 1000K (upper graphs) and 800K (lower graphs).
 
 

(Fig. 2) The graphs show the RDF and a typical surface configuration of the adatoms on the GaAs surface. Now the coverage ratio is 40% of a full layer of GaAs. Again the simulation temperatures were 1000K (upper graphs) and 800K (lower graphs).
 
 

From the RDFs one can read off an island size of 2-5 adatoms for T=1000K and 2-7 adatoms for T=800K. In addition the RDFs for 1000K show a maximum at about 4.8Angstrom which is 2 times the Ga-As distance in a perfect lattice. This indicates that there are no size effects, whereas in the lower temperature case bigger islands tend to "shrink".

Starting from a random distribution of adatoms above the GaAs surface, it can be observed, that As is more likely to escape from the surface than Ga. This is in agreement with experiment. At temperatures above 500°C As sticks to the surface only, if Ga is present in excess [ph1].
 

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