GaN-Based Sensors

High sensitivity label-free detection of HER2 using an Al-GaN/GaN high electron mobility transistor-based biosensor

This work reports rapid, label-free and specific detection of the HER2 antigen using a gallium nitride (GaN) high electron mobility transistor (HEMT). Thiol-based chemistry has been utilized to immobilize the corresponding HER2 antibody in the sensing area of the sensor. The formation of a gold-sulfur complex has been confirmed through Raman spectroscopy, giving a peak at around a wavelength of 260 cm^-1. Fourier transform infrared spectroscopy and atomic force microscopy (AFM) also reveal the functionalization of thiol and free carboxylic groups. On-chip enzyme-linked immunosorbent assay has been utilized to confirm immobilization of antibody receptors on the sensing area surface, followed by current-voltage measurement. Morphology of the sensing area using AFM and electrical characterization of the sensor have been recorded before and after each functionalization process step. The sensor shows detection of the HER2 antigen in a broad range of 0.7 pg ml^-1 to 10 μg ml^-1i.e., (5 × 10^-15 to 6 × 10^-8 M). A long-time study and reusability aspect of the sensor have also been investigated that show good viability of the sensor. For the first time, a three-binding-site model based on the Langmuir isotherm has been developed for HER2 detection using GaN-HEMTs with three dissociation constants, i.e., 7 × 10^-10, 8.8 × 10^-11, and 7.2 × 10^-9 M, respectively.

In(Ga)N Nanostructures and Devices Grown by Molecular Beam Epitaxy and Metal-Assisted Photochemical Etching

This review summarizes the recent research on nitride nanostructures and their applications. We cover recent advances in the synthesis and growth of porous structures and low-dimensional nitride nanostructures via metal-assisted photochemical etching and molecular beam epitaxy. The growth of nitride materials on various substrates, which improves their crystal quality, doping efficiency, and flexibility of tuning performance, is discussed in detail. Furthermore, the recent development of In(Ga)N nanostructure applications (light-emitting diodes, lasers, and gas sensors) is presented. Finally, the challenges and directions in this field are addressed.

Nanowire Chemical/Biological Sensors: Status and a Roadmap for the Future

Chemiresistive sensors are becoming increasingly important as they offer an inexpensive option to conventional analytical instrumentation, they can be readily integrated into electronic devices, and they have low power requirements. Nanowires (NWs) are a major theme in chemosensor development. High surface area, interwire junctions, and restricted conduction pathways give intrinsically high sensitivity and new mechanisms to transduce the binding or action of analytes. This Review details the status of NW chemosensors with selected examples from the literature. We begin by proposing a principle for understanding electrical transport and transduction mechanisms in NW sensors. Next, we offer the reader a review of device performance parameters. Then, we consider the different NW types followed by a summary of NW assembly and different device platform architectures. Subsequently, we discuss NW functionalization strategies. Finally, we propose future developments in NW sensing to address selectivity, sensor drift, sensitivity, response analysis, and emerging applications.