Investigation of electrically active defects at the interface of high-k dielectrics and compound semiconductors

As silicon based devices in integrated circuits reach the fundamental limits of dimensional scaling there is growing research interest in the use of high electron mobility channel materials, such as indium gallium arsenide (InGaAs), in conjunction with high dielectric constant (high-k) gate oxides, for Metal-Oxide-Semiconductor Field Effect Transistor (MOSFET) based devices. The motivation for employing high mobility channel materials is to reduce power dissipation in integrated circuits while also providing improved performance. One of the primary challenges to date in the field of III-V semiconductors has been the observation of high levels of defect densities at the high-k/III-V interface, which prevents surface inversion of the semiconductor. The work presented in this PhD thesis details the characterization of MOS devices incorporating high-k dielectrics on III-V semiconductors. The analysis examines the effect of modifying the semiconductor bandgap in MOS structures incorporating InxGa1-xAs (x: 0, 0.15. 0.3, 0.53) layers, the optimization of device passivation procedures designed to reduce interface defect densities, and analysis of such electrically active interface defect states for the high-k/InGaAs system. Devices are characterized primarily through capacitance-voltage (CV) and conductance-voltage (GV) measurements of MOS structures both as a function of frequency and temperature. In particular, the density of electrically active interface states was reduced to the level which allowed the observation of true surface inversion behavior in the In0.53Ga0.47As MOS system. This was achieved by developing an optimized (NH4)2S passivation, minimized air exposure, and atomic layer deposition of an Al2O3 gate oxide. An extraction of activation energies allows discrimination of the mechanisms responsible for the inversion response. Finally a new approach is described to determine the minority carrier generation lifetime and the oxide capacitance in MOS structures. The method is demonstrated for an In0.53Ga0.47As system, but is generally applicable to any MOS structure exhibiting a minority carrier response in inversion.

The contribution of Victor Hugo to the liberation, emancipation, and changing perceptions of women in 19th century French society

The over-riding perceptions of Victor Hugo’s attitudes towards women are intensely coloured by his deep-seated Romanticism and his well-testified, stifling and over-bearing treatment of women in his personal life. As such, Hugo’s contribution to the feminist struggle of his time has been woefully overlooked in the larger scheme of his social and political activism. Through a close examination of his largely unstudied public discourse on women’s rights, this thesis situates Hugo’s feminist views firmly in the context of Enlightenment feminism and 19th century feminism, while also drawing heavily on the illuminating principles of Enlightenment feminism. In particular, this thesis examines Hugo’s support for several of the most determining issues of 19th century French feminism, including women’s right to education, equal citizenship, universal suffrage rights, and the issue of regulated prostitution. Further, by examining the way in which Hugo’s views on women’s maternal role extended far beyond the limited vision of domesticity bolstered by the ideology of ‘republican motherhood’, this thesis engages in a re-appraisal of Hugo’s literary representation of maternity which identifies the maternal as a universal quality of devotion and self-sacrifice to which all humankind must aspire for the creation of a just, egalitarian, and democratic society. Though at times inevitably constrained by his Romanticism, this thesis demonstrates the extent to which Hugo’s feminism is grounded in his wider vision of social emancipation and is underpinned by a profound empathy, compassion, and moral conscience – qualities which are just as fundamental today, as they were for Hugo when participating in the fitful, though decisive, feminist struggle in 19th century France.