Moïse Sotto

Random telegraph noise from resonant tunnelling at low temperatures

The Random Telegraph Noise (RTN) in an advanced Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) is considered to be triggered by just one electron or one hole, and its importance is recognised upon the aggressive scaling. However, the detailed nature of the charge trap remains to be investigated due to the difficulty to find out the exact device, which shows the RTN feature over statistical variations. Here, we show the RTN can be observed from virtually all devices at low temperatures, and provide a methodology to enable a systematic way to identify the bias conditions to observe the RTN. We found that the RTN was observed at the verge of the Coulomb blockade in the stability diagram of a parasitic Single-Hole-Transistor (SHT), and we have successfully identified the locations of the charge traps by measuring the bias dependence of the RTN.

Random-telegraph-noise by resonant tunnelling at low temperatures

We have found a systematic way to identify the bias conditions to observe the Random-Telegraph-Noise (RTN) in advanced Metal-Oxide-Semiconductor Field-Effect-Transistors (MOSFETs). We measured a p-type MOSFET at 2K, and found narrow bias conditions to observe the RTN presumably caused by charge trapping and de-trapping, which were only observed at low temperatures. It will pave the way to address the nature of a trap, which will be useful to understand the mechanism of RTN to secure the reliability.

Transport properties in silicon nanowire transistors with atomically flat interfaces

We have fabricated ultra-narrow (sub-10 nm) short channel (100 nm) silicon (Si) nanowire transistors with atomically flat interfaces based on Si-on-Insulator (SOI) substrates. The raised source and drain electrodes were patterned together with the gate electrode. The smaller threshold voltage in the narrower nanowire suggests self-limiting oxidation during the gate oxide formation.

Ultrahigh-Q photonic crystal cavities in silicon rich nitride

Ultrahigh-Q Photonic Crystal cavities were realized in a suspended Silicon Rich Nitride (SiNx) platform for applications at telecom wavelengths. Using a line width modulated cavity design we achieved a simulated Q of 520,000 with a modal volume of 0.77(λ/n)3. The fabricated cavities were measured using the resonance scattering technique and we demonstrated a measured Q of 120,000. The experimental spectra at different input power also indicate that the non-linear losses are negligible in this material platform.

Enhanced light emission from improved homogeneity in biaxially suspended Germanium membranes from curvature optimization

A silicon compatible light source is crucial to develop a fully monolithic silicon photonics platform. Strain engineering in suspended Germanium membranes has offered a potential route for such a light source. However, biaxial structures have suffered from poor optical properties due to unfavorable strain distributions. Using a novel geometric approach and finite element modelling (FEM) structures with improved strain homogeneity were designed and fabricated. Micro-Raman (μ-Raman) spectroscopy was used to determine central strain values. Micro-photoluminescence (μ-PL) was used to study the effects of the strain profiles on light emission; we report a PL enhancement of up to 3x by optimizing curvature at a strain value of 0.5% biaxial strain. This geometric approach offers opportunity for enhancing the light emission in Germanium towards developing a practical on chip light source.