Triangular nanoperforation and band engineering of InGaAs quantum wells: a lithographic route toward Dirac cones in III-V semiconductors.

The design of two-dimensional periodic structures at the nanoscale has renewed attention for band structure engineering. Here, we investigate the nanoperforation of InGaAs quantum wells epitaxially grown on InP substrates using high-resolution e-beam lithography and highly plasma based dry etching. We report on the fabrication of a honeycomb structure with an effective lattice constant down to 23 nm by realising triangular antidot lattice with an ultimate periodicity of 40 nm in a 10 nm thick InGaAs quantum well on a p-type InP. The quality of the honeycomb structures is discussed in detail, and calculations show the possibility to measure Dirac physics in these type of samples. Based on the statistical analysis of the fluctuations in pore size and periodicity, calculations of the band structure are performed to assess the robustness of the Dirac cones with respect to distortions of the honeycomb lattice.

Local Schottky contacts of embedded Ag nanoparticles in Al2O3/SiN x :H stacks on Si: a design to enhance field effect passivation of Si junctions.

This paper describes an original design leading to the field effect passivation of Si n+-p junctions. Ordered Ag nanoparticle (Ag-NP) arrays with optimal size and coverage fabricated by means of nanosphere lithography and thermal evaporation, were embedded in ultrathin-Al2O3/SiN x :H stacks on the top of implanted Si n+-p junctions, to achieve effective surface passivation. One way to characterize surface passivation is to use photocurrent, sensitive to recombination centers. We evidenced an improvement of photocurrent by a factor of 5 with the presence of Ag NPs. Finite-difference time-domain (FDTD) simulations combining with semi-quantitative calculations demonstrated that such gain was mainly due to the enhanced field effect passivation through the depleted region associated with the Ag-NPs/Si Schottky contacts.

Trace gas detection with antimonide-based quantum-well diode lasers.

Widely tunable GaInAsSb/AlGaAsSb quantum well (QW) lasers have been grown by molecular beam epitaxy on GaSb substrates. Their emission wavelength, from 2.0 to 2.5 microm, make them suitable for the detection of many gas species in the wavelength range which corresponds to an atmospheric transmission window. Using these devices an experimental setup for open path gas detection has been developed.