Low-Power AlGaN/GaN Triangular Microcantilever for Air Flow Detection.

This paper investigates an AlGaN/GaN triangular microcantilever with a heated apex for airflow detection utilizing a very simple two-terminal sensor configuration. Thermal microscope images were used to verify that the apex region of the microcantilever reached significantly higher temperatures than other parts under applied voltage bias. The sensor response was found to vary linearly with airflow rate when tested over a range of airflow varying from 16 to 2000 sccm.

Infrared Transmission Characteristics of Phase Transitioning VO on Various Substrates.

Infrared transmission characteristics of VO thin films synthesized on multiple substrates, using a low-pressure direct oxidation technique, have been characterized. Material characterization of these films indicates high material quality, which resulted in large variation of electrical and optical properties at phase transition. A change in optical transmissivity greater than 80% was observed for these films utilizing infrared (IR) laser illumination at 1550 nm.

Mechanical memory operations in piezotransistive GaN microcantilevers using Au nanoparticle-enhanced photoacoustic excitation.

Nonlinear oscillations in micro- and nanoelectromechanical systems have emerged as an exciting research area in recent years due to their promise in realizing low-power, scalable, and reconfigurable mechanical memory and logic devices. Here, we report ultralow-power mechanical memory operations utilizing the nonlinear oscillation regime of GaN microcantilevers with embedded piezotransistive AlGaN/GaN heterostructure field effect transistors as highly sensitive deflection transducers. Switching between the high and low oscillatory states of the nonlinear oscillation regime was demonstrated using a novel phase-controlled opto-mechanical excitation setup, utilizing a piezo actuator and a pulsed laser as the primary and secondary excitation sources, respectively.

Voltage triggered near-infrared light modulation using VO thin film.

Development of compact and fast modulators of infrared light has garnered strong research interests in recent years due to their potential applications in communication, imaging, and sensing. In this study, electric field induced fast modulation near-infrared light caused by phase change in VO thin films grown on GaN suspended membranes has been reported. It was observed that metal insulator transition caused by temperature change or application of electric field, using an interdigitated finger geometry, resulted in 7% and 14% reduction in transmitted light intensity at near-infrared wavelengths of 790 and 1550 nm, respectively.

H Detection Using Plasmonically Generated Surface Photoacoustic Waves in Pd Nanoparticle-Deposited GaN Microcantilevers.

Detection of H using plasmonic amplification of surface photoacoustic (SPA) waves generated in Pd nanoparticle-deposited GaN piezotransistive microcantilevers has been investigated using a pulsed 520 nm laser. Using 1.5 nm thickness of the Pd functionalization layer, H detection down to 1.

Investigation of AlGaN/GaN HFET and VO Thin Film Based Deflection Transducers Embedded in GaN Microcantilevers.

The static and dynamic deflection transducing performances of piezotransistive AlGaN/GaN heterojunction field effect transistors (HFET) and piezoresistive VO thin films, fabricated on GaN microcantilevers of similar dimensions, were investigated. Deflection sensitivities were tuned with the gate bias and operating temperature for embedded AlGaN/GaN HFET and VO thin film transducers, respectively. The GaN microcantilevers were excited with a piezoactuator in their linear and nonlinear oscillation regions of the fundamental oscillatory mode.

Photoacoustic Detection of H and NH Using Plasmonic Signal Enhancement in GaN Microcantilevers.

Photoacoustic (PA) detection of H and NH using plasmonic excitation in Pt- and Pd-decorated GaN piezotransistive microcantilevers were investigated using pulsed 520-nm laser illumination. The sensing performances of 1-nm Pt and Pd nanoparticle (NP) deposited cantilever devices were compared, of which the Pd-coated sensor devices exhibited consistently better sensing performance, with lower limit of detection and superior signal-to-noise ratio (SNR) values, compared to the Pt-coated devices. Among the two functionalization layers, Pd-coated devices were found to respond only to H exposure and not to NH, while Pt-coated devices exhibited repeatable response to both H and NH exposures, highlighting the potential of the former in performing selective detection between these reducing gases.

Piezoresistive Graphene/P(VDF-TrFE) Heterostructure Based Highly Sensitive and Flexible Pressure Sensor.

We report on a novel graphene/P(VDF-TrFE) heterostructure based highly sensitive, flexible, and biocompatible pressure/strain sensor developed through a facile and low-cost fabrication technique. The high piezoelectric coefficient of P(VDF-TrFE) coupled with outstanding electrical properties of graphene makes the sensor device highly sensitive, with an average sensitivity of 0.76 kPa, a gauge factor of 445, and signal-to-noise ratio of 60.

High Temperature AlGaN/GaN Membrane Based Pressure Sensors.

A highly sensitive Gallium Nitride (GaN) diaphragm based micro-scale pressure sensor with an AlGaN/GaN heterostructure field effect transistor (HFET) deflection transducer has been designed and fabricated for high temperature applications. The performance of the pressure sensor was studied over a pressure range of 20 kPa, which resulted in an ultra-high sensitivity of ~0.76%/kPa, with a signal-to-noise ratio as high as 16 dB, when biased optimally in the subthreshold region.