Field-effect transistors (FETs) have become eminent electronic devices for biosensing applications owing to their high sensitivity, faster response and availability of advanced fabrication techniques for their production. The device physics of this sensor is now well understood due to the emergence of several numerical modelling and simulation papers over the years. The pace of advancement along with the knowhow of theoretical concepts proved to be highly effective in detecting deadly pathogens, especially the SARS-CoV-2 spike protein of the coronavirus with the onset of the (coronavirus disease of 2019) COVID-19 pandemic. However, the advancement in the sensing system is also accompanied by various hurdles that degrade the performance. In this review, we have explored all these challenges and how these are tackled with innovative approaches, techniques and device modifications that have also raised the detection sensitivity and specificity. The functional materials of the device are also structurally modified towards improving the surface area and minimizing power dissipation for developing miniaturized microarrays applicable in ultra large scale integration (ULSI) technology. Several theoretical models and simulations have also been carried out in this domain which have given a deeper insight on the electron transport mechanism in these devices and provided the direction for optimizing performance.

Optical observation of single-carrier charging in type-II quantum ring ensembles Appl. Phys. Lett. 100, 082104 (2012) High density InAlAs/GaAlAs quantum dots for non-linear optics in microcavities J. Appl. Phys. 111, 043107 (2012) Surface diffusion and layer morphology of ( (112)) GaN grown by metal-organic vapor phase epitaxy J. Appl. Phys. 111, 033526 (2012) Single photon emission from InGaN/GaN quantum dots up to 50K Appl. Phys. Lett. 100, 061115 (2012) Thermal carrier emission and nonradiative recombinations in nonpolar (Al,Ga)N/GaN quantum wells grown on bulk GaN J. Appl. Phys. 111, 033517 (2012) Additional information on J. Appl. Phys. We present a model for the effect of thermal annealing on a single-layer InAs/GaAs quantum dot ͑QD͒ heterostructure and study the corresponding variation in full photoluminescence ͑PL͒ spectrum. In/Ga interdiffusion due to annealing is modeled by Fickian diffusion and the Schrödinger equation is solved separately for electrons and holes to obtain ground state PL peaks of the heterostructure at different annealing temperatures. We theoretically examine the decrease in strain effects and carrier confinement potentials with annealing. PL spectra of the entire ensemble of QDs, annealed at different temperatures, are calculated from a lognormal distribution of QD heights derived from experimental atomic force microscopy ͑AFM͒ data. Results from our calculations, which illustrate the blueshift in emission wavelength and linewidth variation in PL with annealing, are in excellent agreement with experimental PL observations on the same samples. This highlights the potential of the model to assist in precisely engineering the optical properties of QD materials for specific device applications. Moreover, the simplicity of the model and its multiple useful features including computation of material interdiffusion, band profiles and full PL spectra make it a valuable tool to study annealing effects on QD heterostructures.

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Semiconductor nanoparticles with very small size of 2-20 nm (quantum dots) are very much attractive for their excellent photoluminescence property. Therefore, this recent study portrays the green synthesis of highly...

The alteration of electronic properties in chemically modified graphene can be utilized for chemical and biosensing applications. Thus, it is essential to understand how the alteration of density of states and conductance spectra of functionalized zigzag and armchair graphene nanoribbon (GNR) affects its sensitivity. In this aspect, the current–voltage characteristics of GNR based sensors are modeled using the non-equilibrium Green's function method. Our findings show that the presence of chemical moiety at one edge of the zigzag GNR structure opens the bandgap that reduces the current conduction and enhances the sensitivity for detection. However, double edge functionalization restores the semi-metallic character of the zigzag ribbon that reduces the sensitivity. Both single and double edge atomic substitution in armchair ribbon makes it n-type, which shows the alteration in current conduction for detecting the presence of the chemical species. We further found that increasing the width of the ribbon decreases the device sensitivity while it increases for the double edge substituted zigzag structure. The study thus provides essential information and insights into utilizing and operating different edge structures of graphene based sensors for effective detection of chemical and biomolecular species.