Rudrarup Sengupta

Bio: Rudrarup Sengupta is an academic researcher from Indian Institute of Science. The author has contributed to research in topics: Solar cell & Schottky diode. The author has an hindex of 4, co-authored 8 publications receiving 45 citations. Previous affiliations of Rudrarup Sengupta include Heritage Institute of Technology.

Positive Threshold Voltage Shift in AlGaN/GaN HEMTs and E-Mode Operation By ${\mathrm{Al}}_{x}{\mathrm{Ti}}_{1-x}$ O Based Gate Stack Engineering

Abstract: In this paper, for the first time, we have experimentally demonstrated enhancement mode (e-mode) AlGaN/GaN high-electron-mobility transistor (HEMT) operation by integrating p-type high- $\kappa {\mathrm {Al}}_{x}{\mathrm {Ti}}_{1-x}$ O based gate stack. Concentration of Al in Al-Ti-O system was found to be a tuning parameter for the threshold voltage of GaN HEMTs. The high- $\kappa $ properties of ${\mathrm {Al}}_{x}{\mathrm {Ti}}_{1-x}$ O as a function of Al % are studied. Superiority of AlTiO over other p-oxides such as CuO and NiO x is proven statistically. Using the high- $\kappa $ and p-type AlTiO, in conjunction with a thinner AlGaN barrier under gate, 600-V e-mode GaN HEMTs are demonstrated with superior ON-state performance ( $\text{I}_{ \mathrm{\scriptscriptstyle ON}}~\sim ~400$ mA/mm and $\text{R}_{ \mathrm{\scriptscriptstyle ON}} ={8.9}\,\,\Omega $ -mm) and gate control over channel ( $\text{I}_{ \mathrm{\scriptscriptstyle ON}}/\text{I}_{ \mathrm{\scriptscriptstyle OFF}} = {10}^{{7}}$ , SS = 73 mV/dec, and gate leakage <200 nA/mm), beside improved safe operating area reliability.

On the trap assisted stress induced safe operating area limits of AlGaN/GaN HEMTs

Abstract: This experimental study reports a systematic investigation of Safe Operating Area limits in AlGaN/GaN HEMT using sub-μs pulse characterization with on the fly Raman and CV characterization to probe defect and stress evolution across the device. Influence of a recess depth on SOA boundary is analyzed. Post failure analysis corroborates well with the failure physics unveiled in this work.

On the ESD behavior of AlGaN/GaN schottky diodes and trap assisted failure mechanism

Abstract: This experimental study reports ESD behavior of novel designs of GaN Schottky diodes. Impact of electro-thermal transport, device degradation and trap generation on its ESD robustness is analyzed. Role of interface traps in ESD failure of GaN Schottky diode is investigated. Transition from sofit-to-hard failure, which is found to depend on diode area, presence of traps and diode design is discussed. Unique degradation trends, cumulative nature of degradation and trap assisted failure modes are discovered.

Trap Assisted Stress Induced ESD Reliability of GaN Schottky Diodes

Abstract: Electro-thermal behaviour and degradation of recessed GaN Schottky diode are studied under forward and reverse ESD stress. Impact of different surface treatments at Schottky interface, on trap generation and degradation is investigated. Evolution of mechanical stress and defects is probed using onthe-fly Raman spectroscopy. Distinct failure modes are discovered in each case.

Terahertz Impedance Spectroscopy of Biological Nanoparticles by a Resonant Metamaterial Chip for Breathalyzer-Based COVID-19 Prompt Tests

Abstract: We propose a tested, sensitive, and prompt COVID-19 breath screening method that takes less than 1 min. The method is nonbiological and is based on the detection of a shift in the resonance frequency of a nanoengineered inductor–capacitor (LC) resonant metamaterial chip, caused by viruses and mainly related exhaled particles, when performing terahertz spectroscopy. The chip consists of thousands of microantennas arranged in an array and enclosed in a plastic breathalyzer-like disposable capsule kit. After an appreciable agreement between numerical simulations (COMSOL and CST) and experimental results was reached using our metamaterial design, low-scale clinical trials were conducted with asymptomatic and symptomatic coronavirus patients and healthy individuals. It is shown that coronavirus-positive individuals are effectively screened upon observation of a shift in the transmission resonance frequency of about 1.5–9 GHz, which is diagnostically different from the resonance shift of healthy individuals who display a 0–1.5 GHz shift. The initial results of screening coronavirus patients yielded 88% agreement with the real-time quantitative polymerase chain reaction (RT-qPCR) results (performed concurrently with the breath test) with an outcome of a positive predicted value of 87% and a negative predicted value of 88%.

Improving Performances of Enhancement-Mode AlGaN/GaN MIS-HEMTs on 6-inch Si Substrate Utilizing SiON/Al 2 O 3 Stack Dielectrics

Abstract: Enhancement-mode (E-mode) GaN-based MIS-HEMTs still suffer from undeniable gate leakage or low gate breakdown voltage due to the low quality of gate dielectrics, resulting in a notorious tailing effect of the off-state current. In this letter, a gate scheme featuring SiON/Al2O3 stack dielectrics and partially recessed gate barrier has been employed in the AlGaN/GaN MIS-HEMTs. A high on/off current ratio over $10^{{9}}$ and a small threshold voltage ( ${V} _{\text {th}}$ ) hysteresis less than 20 mV are achieved in the fabricated E-mode devices with a ${V} _{\text {th}}$ around 2.5 V, mainly owing to the reduction of the net positive fixed charge density in the SiON/Al2O3 gate stack confirmed by the ${C}$ - ${V}$ measurements. Meanwhile, a good performance uniformity on 6-inch wafer is achieved which demonstrates the promising scheme for fabricating GaN-based E-mode MIS-HEMT products.

Positive Threshold Voltage Shift in AlGaN/GaN HEMTs and E-Mode Operation By ${\mathrm{Al}}_{x}{\mathrm{Ti}}_{1-x}$ O Based Gate Stack Engineering

Abstract: In this paper, for the first time, we have experimentally demonstrated enhancement mode (e-mode) AlGaN/GaN high-electron-mobility transistor (HEMT) operation by integrating p-type high- $\kappa {\mathrm {Al}}_{x}{\mathrm {Ti}}_{1-x}$ O based gate stack. Concentration of Al in Al-Ti-O system was found to be a tuning parameter for the threshold voltage of GaN HEMTs. The high- $\kappa $ properties of ${\mathrm {Al}}_{x}{\mathrm {Ti}}_{1-x}$ O as a function of Al % are studied. Superiority of AlTiO over other p-oxides such as CuO and NiO x is proven statistically. Using the high- $\kappa $ and p-type AlTiO, in conjunction with a thinner AlGaN barrier under gate, 600-V e-mode GaN HEMTs are demonstrated with superior ON-state performance ( $\text{I}_{ \mathrm{\scriptscriptstyle ON}}~\sim ~400$ mA/mm and $\text{R}_{ \mathrm{\scriptscriptstyle ON}} ={8.9}\,\,\Omega $ -mm) and gate control over channel ( $\text{I}_{ \mathrm{\scriptscriptstyle ON}}/\text{I}_{ \mathrm{\scriptscriptstyle OFF}} = {10}^{{7}}$ , SS = 73 mV/dec, and gate leakage <200 nA/mm), beside improved safe operating area reliability.

Photovoltaic Solar Cells: A Review

Abstract: Employing sunlight to produce electrical energy has been demonstrated to be one of the most promising solutions to the world’s energy crisis. The device to convert solar energy to electrical energy, a solar cell, must be reliable and cost-effective to compete with traditional resources. This paper reviews many basics of photovoltaic (PV) cells, such as the working principle of the PV cell, main physical properties of PV cell materials, the significance of gallium arsenide (GaAs) thin films in solar technology, their prospects, and some mathematical analysis of p-n junction solar cells. Furthermore, the paper presents the standard model of solar cells with the application of this model to different PV technologies together with the main findings. Moreover, the paper explores the role of numerical and mathematical modelling of PV cells by MATLAB/Simulink and COMSOL in evaluating the power conversion efficiency (PCE) of the PV cells and determining the main parameters affecting the power output at various conditions.

Localized defect states and charge trapping in atomic layer deposited-Al2O3 films

Abstract: In this study, the authors compared different Al2O3 films grown by atomic layer deposition (ALD) with the same aluminum precursor but on different substrates. The authors employed different process parameters such as thermal-ALD and plasma-enhanced-ALD using different substrate temperatures ranging from 280 °C down to room temperature. They characterized these films by resonant photoelectron spectroscopy and by electrical measurements. They established that generally the ALD-Al2O3 films show characteristic features of bulk Al2O3. For all films investigated, the authors found intrinsic defect states within the electronic band gap and identified excitonic, polaronic, and charge-transfer defect states. The authors gave an atomistic model to explain these intrinsic defects and found that their relative abundance is subject of the choice of ALD parameters and of the substrate used. They were able to relate the spectroscopic assigned in-gap defect states with the electronic charges as determined in our electric...

Understanding the Resistive Switching Phenomena of Stacked Al/Al2O3/Al Thin Films from the Dynamics of Conductive Filaments

Abstract: We present the resistive switching characteristics of Metal-Insulator-Metal (MIM) devices based on amorphous Al2O3 which is deposited by Atomic Layer Deposition (ALD). A maximum processing temperature for this memory device is 300°C, making it ideal for Back-End-of-Line (BEOL) processing. Although some variations in the forming, set, and reset voltages (,, and ) are obtained for many of the measured MIM devices (mainly due to roughness variations of the MIM interfaces as observed after atomic-force microscopy analysis), the memristor effect has been obtained after cyclic measurements. These resistive transitions in the metal oxide occur for both bipolar and unipolar conditions, while the ratio is around 4–6 orders of magnitude and is formed at gate voltages of V. In unipolar mode, a gradual reduction in is observed and is related to combined (a) incomplete dissolution of conductive filaments (made of oxygen vacancies and metal ions) which leaves some residuals and (b) thickening of chemically reduced Al2O3 during localized Joule heating. This is important because, by analyzing the macroscopic resistive switching behavior of this MIM structure, we could indirectly relate it to microscopic and/or nanoscopic phenomena responsible for the physical mechanism upon which most of these devices operate.