Background pressure dependence of GaAs and AlGaAs growth rates in gas-source molecular beam epitaxy

Abstract

The rate of GaAs and AlGaAs epitaxial growth by molecular-beam epitaxy using two gas systems — arsine (AsH 3), triethylgallium (TEG) and Al, and AsH 3, Ga and Al — decreased exponentially as the AsH 3 flow rate increased. We find that growth rate R can be represented using AsH 3 flow rate F as R = B exp(− AF), where A and B are constants. A was the same for GaAs and AlGaAs. In these systems, the background pressure during growth increased from 10 −5 to 10 −4 Torr. In the As 4 and TEG system, the GaAs growth rate was independent of the As 4 beam intensity from 10 −5 to 10 −4 Torr, unlike in the AsH 3 systems. The background pressure in this As 4 pressure range was also constant. We explain these results in terms of an increase of the collision frequency between the group III and background molecules. The value A calculated from our growth conditions using the kinetic theory of gases agreed well with the results of experiments.