Nanoscale Germanium Electronics

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This proposal is a feasibility study to determine the practicality of fabricating nanoscale electronic devices in germanium, of dimensions ranging from tens of nanometres to the atomic scale. The multi-billion pound semiconductor industry is based on integrated circuits (ICs) fabricated on silicon wafers and has been for the last forty years, with components being made smaller by a factor of two every eighteen months (Moore's Law). However, in recent years, the small size of circuit components has introduced a number of troublesome device performance issues due to quantum effects, such as tunnelling, and the incorporation of germanium into device components is seen as a potential solution. One positive aspect of the above mentioned quantum effects, seen in devices approaching nanoscale dimensions, is that new device paradigms which explicitly exploit quantum mechanics are being explored for future generations of ICs and for quantum information processing (QIP) applications. For example there are interesting proposals to make quantum computers from impurities in germanium or from dopants in strained Si-Ge heterostructures. Thus it has become crucial to understand the electrical transport through nanoscale germanium devices and the quantum properties of single and interacting dopants in germanium. In order to provide a clear pathway towards the fabrication of germanium nanoscale dopant devices, techniques will be developed to (i) place dopant atoms at controlled positions in a germanium crystal, with atomic precision, in order to learn about their fundamental properties and (ii) fabricate and electrically characterise buried 1-atom thick dopant layers (delta-doped layers) in germanium. The techniques will utilise a scanning tunnelling microscope (STM), which can image and manipulate matter atom-by-atom, to pattern a single atom thick resist layer made from hydrogen atoms, with a precursor gas supplying the dopants. The same STM will then be used to characterise the fabricated structures.