Dopant Incorporation, Desorption and Migration in MBE Grown InP and AlxGa1-xAs/GaAs

[摘要] The incorporation, desorption and migration behaviour of sulphur and silicon dopants in MBE-grown InP and GaAs/AlGaAs was investigated. Some of the more general aspects of the MBE of InP are also discussed to aid the interpretation of the doping studies. Specifically, data is presented on the calibration of the In and pressures, the stabilisation of InP against the desorption of phosphorus and the sticking coefficient of In at the usual growth temperatures. A thorough study of the effect of growth conditions on the sulphur doping of InP was completed. A sound theoretical framework based on both thermodynamic equilibrium calculations and a kinetic model was developed to enhance the understanding of the incorporation and desorption processes. Thermodynamic calculations are used to identify the desorbing sulphur species, and to show that the activation energy of desorption can be estimated from the thermochemical constants. The kinetic orders of the reactions are deduced from the experimental data. In a related application of thermodynamics, a model for the calculation of the concentrations of native defects was developed. The definition of the virtual reactions is discussed. The available experimental and theoretical thermochemical data is reviewed and used for calculating the defect concentrations. The thesis concludes with a study of silicon migration in modulation doped GaAs/AlGaAs heterostructures. Low temperature Hall measurements of annealed samples were used to show that silicon diffusion can degrade the electron mobility. Evidence is presented of the strong localisation of the 2 dimensional electrons in the unannealed samples.

[发布机构] University:University of Glasgow

[关键词] Materials science, Condensed matter physics