Beyond 5 GHz excitation of a ZnO-based high-overtone bulk acoustic resonator on SiC substrate

This work describes the fabrication and characterization of an Au/ZnO/Pt-based high-overtone bulk acoustic resonator (HBAR) on SiC substrates. We evaluate its microwave characteristics comparing with Si substrates for micro-electromechanical applications. Dielectric magnetron sputtering and an electron beam evaporator are employed to develop highly c-axis-oriented ZnO films and metal electrodes. The crystal structure and surface morphology of post-growth layers have been characterized using X-ray diffraction (XRD), atomic force microscopy (AFM), and scanning electron microscopy (SEM) techniques. HBAR on SiC substrate results in multiple longitudinal bulk acoustic wave resonances up to 7 GHz, with the strongest excited resonances emerging at 5.25 GHz. The value of f.Q (Resonance frequency * Quality factor) parameter obtained using a novel Q approach method for HBAR on SiC substrate is 4.1 * 10^13 Hz which, to the best of our knowledge, is the highest among all reported values for specified ZnO-based devices

Investigation of Structural Parameter Variation on Extended Gate TFET for Bio-Sensor Applications

Traditional Gate engineered Metal Oxide Semiconductor (MOS) technology faced serious challenges in terms of greater sensitivity for target biomolecules and to be utilized as the state-of-the-art Nano-recognition tool. Research on a tunnel field-effect transistor (TFET) started with the aim to achieve fast detection, low power consumption, and its potential for on-chip integration capability. Dielectric Modulated TFET (DMTFET) has established itself to be a primary candidate for sensing both charged and charge-neutral species with volumetric sensitivity. As extended gate DMTFET happens to be inferior to its short gate counterpart, we have devised ways to achieve superior performance only by making variations over structural electrostatics. With the incorporation of most possible ways of modulation, we present two orders of magnitude on-current increment and a considerable percentage of sensitivity improvement over the conventional one. Future scopes having noteworthy diversifications have also been analyzed with proper justification

Ultrafast Green Single Photon Emission from an InGaN Quantum Dot-in-a-GaN Nanowire at Room Temperature

In recent years, there has been a growing demand for room-temperature visible single-photon emission from InGaN nanowire-quantum-dots (NWQDs) due to its potential in developing quantum computing, sensing, and communication technologies. Despite various approaches explored for growing InGaN quantum dots on top of nanowires (NWs), achieving the emission of a single photon at room temperature with sensible efficiency remains a challenge. This challenge is primarily attributed to difficulties in accomplishing the radial confinement limit and the inherent giant built-in potential of the NWQD. In this report, we have employed a novel Plasma Assisted Molecular Beam Epitaxy (PAMBE) growth approach to reduce the diameter of the QD to the excitonic Bohr radius of InGaN, thereby achieving strong lateral confinement. Additionally, we have successfully suppressed the strong built-in potential by reducing the QD diameter. Toward the end of the report, we have demonstrated single-photon emission (${\lambda}$ = 561 nm) at room-temperature from the NWQD and measured the second-order correlation function $g^{2}(0)$ as 0.11, which is notably low compared to other reported findings. Furthermore, the lifetime of carriers in the QD is determined to be 775 ps, inferring a high operational speed of the devices

Molecular beam epitaxy and defect structure of Ge (111)/epi-Gd2O3 (111) /Si (111) heterostructures

Molecular beam epitaxy of Ge (111) thin films on epitaxial-Gd2O3/Si(111) substrates is reported, along with a systematic investigation of the evolution of Ge growth, and structural defects in the grown epilayer. While Ge growth begins in the Volmer-Weber growth mode, the resultant islands coalesce within the first 10 nm of growth, beyond which a smooth two-dimensional surface evolves. Coalescence of the initially formed islands results in formation of rotation and reflection microtwins, which constitute a volume fraction of less than 1 %. It is also observed that while the stacking sequence of the (111) planes in the Ge epilayer is similar to that of the Si substrate, the (111) planes of the Gd2O3 epilayer are rotated by 180 degree about the [111] direction. In metal-semiconductor-metal schottky photodiodes fabricated with these all-epitaxial Ge-on-insulator (GeOI) samples, significant suppression of dark current is observed due to the presence of the Gd2O3 epilayer. These results are promising for application of these GeOI structures as virtual substrates, or for realization of high-speed group-IV photonic components.Comment: 15 pages, 6 figure

Investigation of Magnesium Silicate as an Effective Gate Dielectric for AlGaN/GaN Metal Oxide High Electron Mobility Transistors (MOSHEMT)

In this study, a 6 nm layer of Magnesium Silicate (Mg-Silicate) was deposited on AlGaN/GaN heterostructure by sputtering of multiple stacks of MgO and SiO$_{2}$, followed by rapid thermal annealing in a nitrogen (N$_{2}$) environment. The X-ray photoelectron spectroscopy (XPS) analysis confirmed the stoichiometric Mg-Silicate (MgSiO$_{3}$) after being annealed at a temperature of 850 $^\circ$C for 70 seconds. Atomic force microscopy (AFM) was employed to measure the root mean square (RMS) roughness (2.20 nm) of the Mg-Silicate. A significant reduction in reverse leakage current, by a factor of three orders of magnitude, was noted for the Mg-Silicate/AlGaN/GaN metal-oxide-semiconductor (MOS) diode in comparison to the Schottky diode. The dielectric constant of Mg-Silicate($\mathcal{E}_{Mg-Silicate}$) and the interface density of states (D$_{it}$) with AlGaN were approximated at $\sim$ 6.6 and 2.0 $\times$ 10$^{13}$ cm$^{-2}$eV$^{-1}$ respectively, utilizing capacitance-voltage (CV) characteristics

Dielectric response and impedance spectroscopy of 0.7Pb(Mg<SUB>1/3</SUB>Nb<SUB>2/3</SUB>)O<SUB>3</SUB>-0.3PbTiO<SUB>3</SUB> thin films

Dielectric response of 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-PT) thin films deposited by pulsed laser deposition has been studied as a function of frequency over a wide range of temperatures. The films exhibited maximum frequency dispersion in both real and imaginary part of dielectric susceptibility near and below the dielectric transition temperature. The relaxor behavior in the films was confirmed from the diffused phase transition (DP) together with frequency dependent of transition temperature (Tm). The frequency dependence of transition temperature Tm (temperature of the maximum of dielectric constant) was studied in terms of Vogel-Fulcher relation. The dielectric relaxation of PMN-PT thin films was studied at different temperatures using the complex impedance (Z&#8727;) and electric modulus (M&#8727;) formalism. The shape of complex impedance curve inferred that only one type of dielectric relaxation was involved in the present case. This was attributed to the contribution of bulk grain of the films while the other probable sources, such as grain boundaries, film electrode interfaces were negligible. The films exhibited Debye type dielectric relaxation at temperature sufficiently above the temperature of permittivity maximum (Tm), while a multi-Debye relaxation was observed at lower temperatures (&lt;200 &#176; C), which was confirmed from the broad spectrum of dielectric relaxation. The average relaxation times estimated from Cole-Cole plots varied with temperature according to the V-F relation