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Experimental observations of simultaneous existence of fast and slow trap states in AlGaN/GaN HEMTs are presented here. The presence of traps with time constants (0.1 ms ∼ 0.1 s) and activation energies (0.3 eV∼0.54 eV) was detected from transconductance dispersion and admittance curves. These fast traps may assist the high gate leakage currents in AlGaN/GaN HEMTs. The slower traps having the time...
We have investigated the influence of the reverse transfer conductance Rgd to extract the small signal parameters of GaN high electron mobility transistors (HEMTs) at microwave frequencies. In this paper a simplified method for extracting the small-signal equivalent circuit elements of HEMTs by means of measurements of scattering parameters only is presented. We have calculated the improvement in...
In this paper, we propose a novel methodology of real time dynamic tilt monitoring through the designed and developed Fiber Bragg Grating Tilt Meter (FBGTM). Based on the volumetric water pressure exerted from inside the chamber on the diaphragm over which the FBG sensor is bonded, the tilt angle of FBGTM can be estimated. An inclination platform is constructed to test the designed FBGTM in conjunction...
Deep vertical etching of Si using hydrogen peroxide as oxidant and Au as catalyst has been studied in terms of relative reactant concentrations and catalyst morphology. The concentrations of hydrogen peroxide and hydrofluoric acid are highly important and the ratio of the same can be varied to achieve isotropic to highly anisotropic vertical etching. Catalyst morphology and positioning of the substrate...
In this work, a numerical study is carried out on the effects of localized charges on the threshold voltage of a Tunneling Field Effect Transistor (TFET) using 2D TCAD simulations. The localized charges can be generated at the Si-SiO2 interface by hot carrier effects arising due to high electric fields in the tunneling region of a TFET. The study is carried out with both positive and negative interface...
This paper presents a controlled lateral etching-based technique for realizing nanogap structures. These structures have applications in different bio-medical/ biochemical sensors. The sensitivity of such sensors depends on the gap size. The method method uses single mask lithography, followed by etching for the first electrode material and lift-off for the second electrode material. Controlled under-etching...
We propose an index tuned silicon photonic sensor capable of measuring refractive indices of liquid analytes. This sensor uses two microring resonators in cascaded configuration. Conventional double microring resonators display high sensitivity but limited range of detection. We show that the range of detection can be enhanced by more than an order of magnitude by using index tuning.
Graphene is considered one of the most promising materials for future electronics as it exhibits high charge carrier mobility. The prerequisite for the development of graphene-based electronics is to dope graphene effectively. In general, graphene-based field effect transistors show unwanted and uncontrolled p-type behavior in the ambient. It is required to dope graphene controllably without affecting...
In this work, we report the dependence of optimum value of field plate parameters, viz., overlap length and dielectric thickness, on dielectric constant of field-plate dielectric in a 1900V, Ni/4H-SiC Schottky diode. Field plate overlap length and dielectric thickness are optimized for different device processing-compatible dielectric materials: SiO2, Si3N4, Al2O3 and HfO2. The results show that the...
Bimorph cantilever-based thermal actuators are promising for numerous applications like micro-mirror arrays, etc. This paper presents a simple technique for fabricating bimorph cantilevers using a single photolithography process and a quick optical methodology for the characterization of such structures. A bimorph combination of Al-SiO2 has been realized where SiO2 cantilevers are first realized,...
Charge carrier mobility is a critical parameter in organic field effect transistors and it is strongly influenced by morphology and structure of the involved organic materials. In this work, we present a study on impact of grain size and surface roughness of the active layer on the mobility in top gate n-type C60 organic field effect transistors. The morphology was varied by changing the substrate...
AlGaN/GaN HEMTs were post-gate-annealed at 300°C for 2 min and longer. DC characteristics of AlGaN/GaN HEMTs as a function of annealing cycle duration were studied. Improvement in HEMT parameters such as drain source saturation current, transconductance, gate leakage current and off-state breakdown voltage (Vboff) was observed with increase in annealing duration. This was correlated with surface/interface...
SiGe thin layers were deposited using LPCVD at different temperatures and pressures. The effect of the growth characteristics on the composition, grain growth and crystallinity were studied with the aim of maximizing the tensile stress of the films deposited. As expected, at constant reactant gas ratios, temperature had the maximum effect, with stress changing from compressive to tensile at higher...
In this paper, we propose and investigate a novel device structure for silicon-on-ferroelectric Tunnel FET (SOFTFET) based on the negative capacitance effect of the ferroelectric layer. The conduction mechanism of proposed device is based on the combined effect of two mechanisms namely, tunnelling and negative capacitance effect. Thus, it achieves a steep subthreshold slope (SS) of 13.9 mV/dec at...
Higher on-current (Idsat) and lower off-current (Ioff) can be achieved through dynamic threshold voltage (Vth) in MOSFETs. The change in Vth with gate bias is usually achieved through the body effect by connecting the gate terminal to the substrate in MOSFETs with heavily doped substrates. In this paper, we report the presence of dynamic Vth even in FinFETs with undoped channels. In this case, the...
We present a physical compact model for the calculation of the capacitance including a physics based model for the calculation of the charge centroid for III-V FETs. We have used Fermi-Dirac statistics considering two energy subbands obtained from analytical Schrödinger-Poisson solution of charge. The model is validated with data from numerical device simulations and shows excellent match.
The changes in dc characteristics of AlGaN/GaN HEMT after ICP-CVD silicon nitride (SiNx) passivation using two different recipes were investigated. Room temperature Raman analysis was performed to determine the stress state of the AlGaN layer after SiNx passivation. The changes in the stress state of the device after passivation was correlated with the shift in threshold voltage and changes in drain...
200 nm thick films of gallium nitride were grown on sapphire substrate using molecular beam epitaxy. Gold nanoparticles were fabricated on the grown films by thermal evaporation followed by annealing. Aluminium nanostructures were fabricated on another set of films using nanosphere lithography. Interdigited electrodes were fabricated using standard lithography to form metal-semiconductor-metal photodetectors...
A physics-based, charge-based model for P-type Gaussian doped DG MOSFET is presented in this work. The developed model is also applicable to the investigation of the impact of channel material on the performance of p-type DG MOSFET. The reliability issues of the p-type MOSFET have also been demonstrated using both developed analytical model and simulated results. The performance degradation due to...
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