The effects of growth kinetics and thermodynamics on the properties of gallium nitride grown by molecular beam epitaxy

The role of thermodynamic and kinetic processes in the growth of GaN by molecular beam epitaxy is investigated. A review of the thermodynamic properties of GaN as well as the other constituents in the growth system is presented. Due to a lack of existing experimental data, the Gibb's energy of GaN is estimated over a wide temperature range determining the heat capacity from chemical trends. The resulting temperature dependent entropy as calculated from this heat capacity combined with the third law of thermodynamics is in excellent agreement with published measurements of the Gibb's energy of formation of GaN at high temperature. This empirical approach enables extrapolation of these high temperature data to MBE growth conditions with a high degree of confidence.; Kinetic processes are examined during growth using reflection high energy electron diffraction (RHEED) and desorption mass spectroscopy (DMS). We find that the incorporation rate of NH{dollar}sb3{dollar} during growth is reduced when excess Ga accumulates on the surface. In the absence of this accumulated Ga, NH{dollar}sb3{dollar} incorporation is not kinetically limited for typical MBE conditions. Langmuir evaporation measurements of GaN are also reported and agree with previously published data for free Langmuir evaporation. When Ga flux is incident on the substrate surface, the decomposition rate decreases according to a mass-action law.; The buffer layer plays a key role in determining both the optical and electrical properties of the GaN films. Growth using a thin, low temperature AlN buffer layer leads to insulating films with reduced defect related luminesence. Films grown with thicker buffer layers at higher temperature are conducting and exhibit higher deep level luminesence intensity. Room temperature Hall mobilities in conducting films did not exceed 140 {dollar}rm cmsp2Vsp{lcub}-1{rcub}ssp{lcub}-1{rcub}{dollar} with typical carrier concentrations of about {dollar}rm 10sp{lcub}18{rcub}cmsp{lcub}-3{rcub}{dollar}.