SIMULATION STUDIES OF GE SURFACE SEGREGATION DURING GAS-SOURCE MBE GROWTH OF SI/SI1-XGEX HETEROSTRUCTURES

Simulation studies of Ge surface segregation have been made and compared to experimental results during gas source MBE (GSMBE) of Si/Si1-xGex heterostructures. Segregation kinetics were examined through simulations using a two-site exchange model. The influence of surface hydrogen during GSMBE was investigated in terms of the energy parameters in the model; specifically, the kinetic barrier height, E1, and the Gibbs heat of segregation, DELTAG(seg). Results indicate that the addition of surface hydrogen to the system suppresses segregation due to a lowering of the apparent Gibbs heat of segregation, rather than increasing the kinetic barrier. Simulations were also performed to study the relative bulk and surface Ge concentrations, an important consideration when comparing in situ RHEED intensity oscillation data, which measures solely surface phenomena, with ex situ techniques such as SIMS which measure the final static concentration profile following growth.