Robin Nicholas

Abstract:

Measurements of Shubnikov-de Haas oscillations in the semiconducting perovskite KTaO//3 have been studied as a function of crystallographic orientation and temperature. The two oscillatory periods observed for all directions except B parallel (111) were found to correspond to ellipsoidal constant energy surfaces located at the X-point. The temperature dependence of the Shubnikov-de Haas amplitudes was used to determine effective masses, m//t equals 0. 61 m//o and m//1 equals 1. 4 m//o.

Abstract:

The effective mass of electrons in InAs//1// minus //xP//x has been determined as a function of alloy composition by cyclotron resonance and the magnetophonon effect. Comparison with k. p theory shows a reduction in the matrix element P**2 due to alloy disorder. Magnetophonon oscillations were observed due to both of the L. O. phonon modes present in the mixed crystals.

Abstract:

Magnetophonon resonance, Shubnikov-de Haas oscillations, cyclotron resonance and Raman effect have been used to determine the effective masses and phonon energies in Ga//xIn//1// minus //xAs//yP//1// minus //y epitaxial layers. For x equals 0. 12, y equals 0. 23 m*** equals 0. 072, which is 20% larger than a previously reported value. The experimentally determined masses are approximately 10% larger than the values predicted by k. p theory, indicating a decrease in the momentum matrix element P**2.