Rolled-Up Nanotech: Illumination-Controlled Hydrofluoric Acid Etching of AlAs Sacrificial Layers

<p>Abstract</p> <p>The effect of illumination on the hydrofluoric acid etching of AlAs sacrificial layers with systematically varied thicknesses in order to release and roll up InGaAs/GaAs bilayers was studied. For thicknesses of AlAs below 10 nm, there were two etching regimes for the area under illumination: one at low illumination intensities, in which the etching and releasing proceeds as expected and one at higher intensities in which the etching and any releasing are completely suppressed. The &#8220;etch suppression&#8221; area is well defined by the illumination spot, a feature that can be used to create heterogeneously etched regions with a high degree of control, shown here on patterned samples. Together with the studied self-limitation effect, the technique offers a way to determine the position of rolled-up micro- and nanotubes independently from the predefined lithographic pattern.</p

Multiple release layer study of the intrinsic lateral etch rate of the epitaxial lift-off process

Contains fulltext : 58642.pdf (publisher's version ) (Closed access)The lateral etch rate of AlGaAs in HF in the 'Epitaxial Lift-Off' (ELO) process consists of two parts, an intrinsic and a radius-induced part. The intrinsic part is studied with a new approach in which multiple release layers are introduced in one sample. By letting an essential ELO process parameter vary over the different release layers, this parameter is examined, using only samples from one wafer. In this study, the influence of thickness, aluminium fraction, and doping concentration of the release layer on the lateral etch rate is investigated. For release layers with thicknesses below 10 nm, a positive correlation between thickness and intrinsic etch rate is found. Thicker release layers do not result in higher etch rates. Increasing aluminium fractions in the AlxGa1-xAs release layers result in higher etch rates. For aluminium fractions between 0.3 and 1, this effect covers almost six orders of magnitude. From the width of the V-shaped etch slits in samples that have been etched for 12 hours or more, the selectivity, i.e., the ratio of the etch rate of AlxGa1-xAs to GaAs, is determined. Selectivities between 4.3 and 8.6x10(5) are found for x=0.3 and x=1, respectively. A variation in silicon doping is found to have no effect on the lateral etch rate, while increased zinc doping raises the etch rate significantly