Putting pn junctions to work: silicon micro-/nano-mechanical devices based on depletion region actuators and sensors

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A research program for the systemic study of the behaviour and applications of semiconductor pn junctions for transduction at micro- and nano-scales is proposed. When a pn junction is formed, majority carriers from either side of the junction diffuse into the opposite side, leaving behind ionised acceptor and donor atoms that are fixed within the semiconductor lattice. This gives rise to a Coulombic body force between the two sides of a pn junction, which can be modulated by an external voltage. As expected, this force is rather small and has been largely ignored. Employing mechanical resonance allows for effective amplification of this force by as much as six orders of magnitude, making it suitable for many applications of microdevices. The proposal discusses the advantages of pn junction actuation over other transduction mechanisms at micro- and nano-scales and demonstrates that pn junction actuators present an unexploited potential to revolutionise microsystem design and application. The holistic approach of the proposed research program deepens our understanding of the operating principles of pn junction actuators while devising practical device design methods. Existing models for pn junction actuators are applicable only to the simplest of cases. We will develop realistic device models that will be verified using experimental data from fabricated test structures and devices. The models will then be employed to design microdevices for timing, sensing, and signal processing applications. Lowering the device dimensions to nano-scales opens up many scientific and technical opportunities. On one hand, pn junction actuation provides an efficient transduction mechanism at nano-scales, leading the way to the development of nano-mechanical devices for daily applications. On the other hand, the small dimensions of nano-devices provide research opportunities to study the operation of pn junction actuators at extreme cases such as fully depleted structures. Doping is a basic process in microelectronics. It is therefore possible to fabricate micromechanical devices based on pn junction actuators in standard integrated circuit manufacturing processes, and as is shown, without a need for any additional steps. This will allow for co-fabrication of microelectronic and micromechanical devices in any standard foundry process. My research team has expertise on the design of micromechanical resonators, microsensors, nanocomposite materials, and microelectronic circuits. Our laboratory is equipped with all the necessary tools for the electrical characterisation of the micro- and nano-mechanical. Additionally, SFU houses two fully equipped cleanrooms for the fabrication of micro- and nano-devices. We are therefore in an ideal position to leverage our expertise to conduct the proposed research, which will revolutionise the field. Collaborations with Canadian and international researchers exposes the involved HQP to the wider academic and industrial community. The HQP trained over the course of this program will be the leading researchers and entrepreneurs who will transform the scientific and technological achievements of this program into novel solutions in the area of micro- and nano-systems. This research has an immediate impact on the field leading to substantial scientific, technical, and industrially relevant outcomes. Device design methodologies developed through this program can be applied to the design of numerous novel micro- and nano-devices for different applications. Considering that the required resources for device design and fabrication are commercially available, this pioneering research will result in significant economic benefit to the Canadian industry and society in the near term.