Stoichiometry control of compound semiconductor crystals. Pt. 2

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 vapour pressure is also obtained from both the annealing and liquid phase epitaxial (LPE) 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 (IAs) in GaAs is emphasised. From the recent capacitance 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. Mechanism of stoichiometry control is discussed on the basis of the equality of chemical potentials and the change of saturating solubility in the liquidus phase as a function of the vapour pressure. Stoichiometry-control should be also important in the field of the superconducting ceramics. (author). 5 refs, 16 refs