Molecular Beam Epitaxy Conditions Research Articles

The Interplay of Thermodynamics and Kinetics in Molecular Beam Epitaxy (MBE) of Doped Gallium Arsenide

Molecular beam epitaxy (MBE) is normally carried out with a substantial overpotential for growth. The generally accepted assumption, that as a consequence the thermodynamic framework describing chemical equilibrium is irrelevant, has been reexamined. The thermodynamic predictions for the behavior of the common dopants Si, Ge, Sn, Pb, Be, Mn, S, Se, Te, Zn, Cd, and Mg in under typical MBE conditions have been determined. Good agreement with observed behavior is found for all cases except Pb. Thus it is shown that when doping is unsuccessful it is because there is no overpotential for doping, even though the overpotential for growth of is maintained. The results show that there is no clear evidence for major kinetic barriers in MBE of , only the possibility of subtler effects of the kind found in VPE and LPE. The method should be predictive in the application of MBE to new systems.

MBE-grown insulating oxide films on GaAs

The technique of molecular beam epitaxy (MBE) has been used to grow two types of insulating oxide films on the surface of GaAs active layers; (i) a native oxide and (ii) an amorphous aluminium oxide, respectively. Native oxides on (100) GaAs obtained by thermal oxidation at 400°C under MBE conditions were found to be suitable for masking purposes and pattern generation because of their favorable mechanical and interface properties. Insulating amorphous aluminium oxide films were grown by molecular beam reaction on an intermediate AlxGa1−xAs layer, in order to preserve the stoichiometry of the GaAs active layer surface. The initial measurements on Al/Al2O3/Al0.35Ga0.65As/GaAs MOS capacitors have shown that favorable mechanical and insulating behavior can be obtained with Al2O3 layers grown at low temperatures and that the properties are sufficiently promising to investigate the MOS device potential of these Al2O3/AlxGa1−xAs/GaAs heterostructures.