ITR: Materials for InAs MOSFETs: The Enabling Transistor for Low Power, 100 GHz+ Information Transfer and Processing

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This project addresses atomic and electronic structures formed by a series of vapor deposited oxides onto antimony based semiconductor alloys, "ABCS" (InAs, GaSb, AlSb, and their alloys); the aim is to achieve understanding of basic mechanisms of Fermi level unpinning of oxide-ternary semiconductor interfaces. Related interfacial chemistry issues need to be sufficiently understood to allow prediction of which oxides are best candidates to form unpinned interfaces on channels and confinement layers in InAs device structures. It is conjectured that to grow an unpinned oxide-ABCS interface, sub-oxide molecules insert into surface dimers, break the surface reconstruction, restore the bulk crystal symmetry, and passivate the oxide/semiconductor interface. Three tasks are envisioned: Task 1: To determine the best combinations of sub-oxides (Al2O, Ga2O, In2O, Tl2O, SiO, GeO, TiO) and "ABCS" surfaces (AlSb, GaSb, InAs or their alloys) for passivation, calculations will be performed on a series of sub-oxides and surfaces. These calculations will ensure that each candidate sub-oxide breaks the dimer reconstruction, unpins the Fermi level, and does not displace dimer atoms. This has been done successfully for Ga2O/GaAs. Task 2: To determine the optimal reconstruction and temperature for deposition of sub-oxide-surface combinations identified in Task 1, combinatorial film growth will be used. Sub-oxides will be vapor deposited onto atomically clean, ordered surfaces. Scanning tunneling microscopy (STM) and spectroscopy (STS) will be employed to determine both the atomic and electronic structure of the surface after deposition and without exposure to air. Deposition will be tested on several surface reconstructions. Task 3: A thick (30 to 100A) layer of an insulating gate oxide compatible with the suboxide developed in Task 1 will be deposited on the best oxide-semiconductor surfaces and capacitance and transconductance measurements will be made to characterize the oxide-semiconductor interface. This work will utilize the expansive knowledge base of the NRL in InAs HEMT processing and InAs/GaAs wafer growth. Additionally, all circuit testing will be done by collaboration with Motorola. %%% An important impact of the project is in education and human resource development through the integration of research and education. The multi-disciplinary nature of the research where students work in chemistry, physics, or electrical engineering departments provides broad educational opportunities. Special efforts are made to ensure the diversity of students working on the project through summer program activities. To foster student-industrial relations the PI also directs an industrial interaction day bringing together UCSD graduate students working in materials chemistry, physics, and engineering and recent graduates working in industry (Intel, LSI, IBM, HRL, Agilent, Applied Materials, and Novacrystals). The day consists of talks that are given by students and industrial scientists. Technological relevance to ITR (Information Technology Research) includes wireless communication, remote sensor networks, personal digital assistants, and mm-wave imaging arrays, as well as high frequency (100 GHz) logic, micro air vehicles with sensors and telemetry (for detection of environmental pollutants and chemical/biological warfare agents), and microscopic sensors with local signal processing (either for chemical/biological weapons detection or for subdermal implantation for medical diagnostics). These devices all require high speed, low power logic enabled by the research activities of this project with particular relevance to the ITR goals of delivery of critical information anytime, anywhere and optimization of work efficiency. ***