A fully integrated GaAs-based three-axis Hall magnetic sensor exploiting self-positioned strain released structures

In this work, we demonstrate a fully integrated three-axis Hall magnetic sensor by exploiting microfabrication technologies applied to a GaAs-based heterostructure. This allows us to obtain, by the same process, three mutually orthogonal sensors: an in-plane Hall sensor and two out-of-plane Hall sensors. The micromachined devices consist of a two-dimensional electron gas AlGaAs/InGaAs/GaAs multilayer which represents the sensing structure, grown on the top of an InGaAs/GaAs strained bilayer. After the release from the substrate, the strained bilayer acts as a hinge for the multilayered structure allowing the out-of-plane self-positioning of devices. Both the in-plane and out-of-plane Hall sensors show a linear response versus the magnetic field with a sensitivity for current-biased devices higher than 1000 V A−1 T−1, corresponding to an absolute sensitivity more than 0.05 V T−1 at 50 µA. Moreover, Hall voltage measurements, as a function of the mechanical angle for both in-plane and out-of-plane sensors, demonstrate the potential of such a device for measurements of the three vector components of a magnetic field

02/28/1984 - Cager Could Come Up With Upset

We propose the realization of a compact fully-passive biotelemetry tag composed of a high-electron mobility transistor (HEMT) connected to a wireless link. The Gallium Arsenide based gateless HEMT serves both as the environmental sensing element and as the amplitude modulator of the carrier signal received by the antenna. A prototype demonstrator operating in the MHz range has been developed: it consists of an array of transistors with different gate geometries and two spiral loop resonators implementing the wireless link. More specifically, one resonator (Tag-resonator) is connected to the array of transistors, while the other one (Reader-resonator) is connected to a power generator/reader device; the wireless link uses the magnetic coupling between the two resonators. Experimental results demonstrate that the reader-resonator exhibits an intensity modulation of the resonance dip depending on the voltage applied to the HEMT gate. These results will be used as a guideline for the realization of biocompatible sub-millimeter tags operating in the Gigahertz frequency range

Fabrication of multipoint light emitting optical fibers for optogenetics

Multipoint Light Emitting Optical Fibers (MPF) has been recently demonstrated as a versatile tool for spatially addressable optogenetics experiments. Their fabrication has been possible thanks to a number of key microfabrication technologies, in particular the unique nanofabrication capabilities of a Focused Ion Beam. This work provides the complete description of MPF fabrication, detailing the optimization process for each fabrication step

Gallium arsenide passivation method for the employment of High Electron Mobility Transistors in liquid environment

We report on effective prevention of GaAs corrosion in a cell culture liquid environment by means of polymerized (3-mercaptopropyl)-trimethoxysilane thin film coatings. Aging in physiological solution kept at 37 °C revealed no significant oxidation after 2 weeks, which is the typical period of incubation of a neuron cells culture. The method was also applied to High Electron Mobility Transistors (HEMT) arrays with unmetallized gate regions, in view of their application as neural signal transducers. Significant reduction of the degradation of the HEMT behavior was obtained, as compared to uncoated HEMTs, with good channel modulation efficiency still after 30 days aging