The piezoelectric effect in II-VI semiconductors

Abstract

This thesis explores the nature and application of the piezoelectric effect in ZnSe-based semiconductors, and also includes a chapter on microscope analysis techniques. Photoelectrochemical etching of ZnSe is shown to reveal defect sites that are related to features observed by a technique of luminescence microscopy. The defect densities are related to the optical quality of the material. Defect annealing under intense optical excitation has been observed. The piezoelectric effect produces an internal electric field that shifts inter-band transitions to lower energies by the quantum confined Stark effect. Previous experiments of photocurrent on the piezoelectric effect in ZnCdSe / ZnSe quantum wells are expanded and improved on and with similar results obtained by photoluminescence excitation, provide a method of measuring the internal field. Photoluminescence experiments reveal the effect of the internal field on the free and donor bound excitons, as well as the exciton localisation. Finally the piezoelectric effect is utilised to find the critical thickness of the start of strain relaxation in ZnCdSe / ZnSe quantum wells, as the internal field is directly proportional to the strain in the well layer.