Studies of scandium-germanium systems and studies of zinc and selenium doped gallium arsenide

This investigation is concerned with a study of the properties of scandium-germanium systems, and a study of the properties of selenium and zinc doped gallium arsenide„ In part one the physical properties of scandium and germanium are used to empirically estimate the relative solubility of scandium in germanium. It was shown that scandium and germanium are miscible in the liquid phase and that scandium has a very low solid solubility in germanium. Crystals of scandium-doped germanium were grown and analyzed using Hall constant and resistivity measurements from liquid nitrogen temperature to room temperature. The results show that the crystals grown are p-type, but that this behaviour cannot be completely attributed to scandium. However, it was shown that if scandium does not form compounds on crystal growth, it has a maximum solubility in germanium of less than one part per million. Methods for analysing the results of experimental measurements, to determine the concentration of acceptors, donors and free carriers, and the ionization energies are given. In part two the properties of selenium and zinc doped gallium arsenide were studied, again using resistivity and Hall measurements. Selenium and zinc were determined to be shallow donors and acceptors respectively. The concentration of the impurities present were determined and the properties of the material were discussed.Science, Faculty ofPhysics and Astronomy, Department ofGraduat