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Si/SiGe resonant interband tunnel diodes were fabricated using chemical vapor deposition (CVD) on 200-mm diameter p-doped silicon wafers. The resonant interband tunnel diode structure consists of a p+-i-n+ diode that incorporates vapor phase doped δ-doping to enhance quantum mechanical tunneling probability. The tunneling barrier thickness is varied from 2 nm to 8 nm, and a record peak-to-valley current ratio of 5.2 for a CVD process is reported for a 6 nm barrier thickness with a room temperature peak tunneling current of 20 A/cm2. The current density increases exponentially with spacer thickness reduction with a maximum value of 280 A/cm2 for a 2 nm barrier.

Protein detection using biologically or immunologically modified field-effect transistors (bio/immunoFETs) depends on the nanoscale structure of the polymer/protein film at sensor interfaces (Bhushan 2010 Springer Handbook of Nanotechnology 3rd edn (Heidelberg: Springer); Gupta et al 2010 The effect of interface modification on bioFET sensitivity, submitted). AlGaN-based HFETs (heterojunction FETs) are attractive platforms for many protein sensing applications due to their electrical stability in high osmolarity aqueous environments and favourable current drive capabilities. However, interfacial polymer/protein films on AlGaN, though critical to HFET protein sensor function, have not yet been fully characterized. These interfacial films are typically comprised of protein–polymer films, in which analyte-specific receptors are tethered to the sensing surface with a heterobifunctional linker molecule (often a silane molecule). Here we provide insight into the structure and tribology of silane interfaces composed of one of two different silane monomers deposited on oxidized AlGaN, and other metal oxide surfaces. We demonstrate distinct morphologies and wear properties for the interfacial films, attributable to the specific chemistries of the silane monomers used in the films. For each specific silane monomer, film morphologies and wear are broadly consistent on multiple oxide surfaces. Differences in interfacial film morphology also drive improvements in sensitivity of the underlying HFET (coincident with, though not necessarily caused by, differences in interfacial film thickness). We present a testable model of the hypothetical differential interfacial depth distribution of protein analytes on FET sensor interfaces with distinct morphologies. Empirical validation of this model may rationalize the actual behaviour of planar immunoFETs, which has been shown to be contrary to expectations of bio/immunoFET behaviour prevalent in the literature for the last 20 years. Improved interfacial properties of bio/immunoHFETs have improved bio/immunoHFET performance: better understanding of interfaces may lead to mechanistic understanding of FET sensor properties and to clinical translation of the immunoFET platform.

This is the first report of a Si/SiGe resonant interband tunneling diodes (RITDs) on silicon substrates grown by the chemical vapor deposition process. The nominal RITD structure forms two quantum wells created by sharp δ-doping planes which provide for a resonant tunneling condition through the intrinsic spacer. The vapor phase doping technique was used to achieve abrupt degenerate doping profiles at higher substrate temperatures than previous reports using low-temperature molecular beam epitaxy, and postgrowth annealing experiments are suggestive that fewer point defects are incorporated, as a result. The as-grown RITD samples without postgrowth thermal annealing show negative differential resistance with a recorded peak-to-valley current ratio up to 1.85 with a corresponding peak current density of 0.1 kA/cm 2 at room temperature.

Si-based nanowires with high aspect ratios have been fabricated using an inductively coupled plasma reactive ion etching ͑ICP-RIE͒ with a continuous processing gas mixture of fluorine-based SF 6 :C 4 F 8 combined with a thermal oxidation technique. The subsequent thermal oxidation further reduced the nanowire diameter utilizing the self-limiting oxidation effect below the lithographic dimensions. Transmission electron microscopy analysis of the completed nanostructures revealed the total oxide thickness and the consumption of the Si core which determines the inner nanowire diameter. The final dimensions of the inner Si nanowire are about 600 nm tall and less than 25 nm wide using top-down processing techniques.