The aggressive reduction of feature size in silicon (Si)-based complimentary metal-oxide-semiconductor (CMOS) technology has resulted in an exponential increase in computing power. Stemming from increases in device density and substantial progress in materials science and transistor design, the integrated circuit has seen continual performance improvements and simultaneous reductions in operating power (VDD). Nevertheless, existing Si-based metal-oxide-semiconductor field-effect transistors (MOSFETs) are rapidly approaching the physical limits of their scaling potential. New material innovations, such as binary group IV or ternary III-V compound semiconductors, and novel device architectures, such as the tunnel field-effect transistor (TFET), are projected to continue transistor miniaturization beyond the Si CMOS era. Unlike conventional MOSFET technology, TFETs operate on the band-to-band tunneling injection of carriers from source to channel, thereby resulting in steep switching characteristics. Furthermore, narrow bandgap semiconductors, such as germanium (Ge) and InxGa1-xAs, enhance the ON-state current and improve the switching behavior of TFET devices, thus making these materials attractive candidates for further study. Moreover, epitaxial growth of Ge on InxGa1-xAs results in tensile stress (ε) within the Ge thin-film, thereby giving device engineers the ability to tune its material properties (e.g., mobility, bandgap) via strain engineering and in so doing enhance device performance. For these reasons, this research systematically investigates the material, optical, electronic transport, and heterointerfacial properties of ε-Ge/InxGa1-xAs heterostructures grown on GaAs and Si substrates. Additionally, the influence of strain on MOS interfaces with Ge is examined, with specific application toward low-defect density ε-Ge MOS device design. Finally, vertical ε-Ge/InxGa1-xAs tunneling junctions are fabricated and characterized for the first time, demonstrating their viability for the continued development of next-generation low-power nanoelectronic devices utilizing the Ge/InxGa1-xAs material system. / Doctor of Philosophy / The aggressive scaling of transistor size in silicon-based complimentary metal-oxide-semiconductor technology has resulted in an exponential increase in integrated circuit (IC) computing power. Simultaneously, advances in materials science, transistor design, IC architecture, and microelectronics fabrication technologies have resulted in reduced IC operating power requirements. As a consequence, state-of-the-art microelectronic devices have computational capabilities exceeding those of the earliest super computers at a fraction of the demand in energy. Moreover, the low-cost, high-volume manufacturing of these microelectronic devices has resulted in their nigh-ubiquitous proliferation throughout all aspects of modern life. From social engagement to supply chain logistics, a vast web of interconnected microelectronic devices (i.e., the "Internet of Things") forms the information technology bedrock upon which 21st century society has been built. Hence, as progress in microelectronics and related fields continues to evolve, so too does their impact on an increasingly dependent world.
Moore's Law, or the doubling of IC transistor density every two years, is the colloquialism used to describe the rapid advancement of the microelectronics industry over the past five decades. As mentioned earlier, parallel improvements in semiconductor technologies have spearheaded great technological change. Nevertheless, Moore's Law is rapidly approaching the physical limits of transistor scaling. Consequently, in order to continue improving IC (and therefore microelectronic device) performance, new innovations in materials and fabrication science, and transistor and IC designs are required. To that end, this research systematically investigates the material, optical, and electrical properties of novel semiconductor material systems combining elemental (e.g., Germanium) and compound (e.g., Gallium Arsenide) semiconductors. Additionally, alternative transistor design concepts are explored that leverage the unique properties of the aforementioned materials, with specific application to low-power microelectronics. Therefore, through a holistic approach towards semiconductor materials, devices, and circuit co-design, this work demonstrates, for the first time, novel transistor architectures suitable for the continued development of next-generation low-power, high-performance microelectronic devices.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/117965 |
| Date | 12 February 2024 |
| Creators | Clavel, Michael Brian |
| Contributors | Electrical Engineering, Hudait, Mantu K., Heremans, Jean Joseph, Orlowski, Mariusz Kriysztof, Jia, Xiaoting, Lester, Luke F. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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