Stoichiometry control of compound semiconductor crystals

Effects of stoichiometry on various feature of III-V compounds are investigated. The application of the optimum vapour pressure of group V elements is shown to minimize the deviation from the stoichiometric composition. Temperature dependence of the optimum vapor pressure is also obtained from both the annealing and the liquid phase epitaxial growth experiments.Vapour pressure technology is successfully applied to the bulk crystal growth. In view of the defect formation mechanism, role of the stable interstitial As atoms in GaAs is emphasized. From the recent photocapacitance results, it is also shown that the excess group V atoms is also important for the formation of stoichiometry dependent deep levels in InP and AlGaAs crystals. Even in the research field of surface science it is shown that the precise control of stoichiometric composition should be required. (author)