Department of Electrical Engineering

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IIT Jodhpur

In part I of this paper, we developed physical insights into the role and impact of acceptor and donor traps - resulting from C-doping in GaN buffer - on avalanche breakdown in AlGaN/GaN HEMT devices. It was found that the donor traps are mandatory to explain the breakdown voltage improvement. In this paper, silicon doping is proposed and explored as an alternative to independently engineer donor trap concentration and profile. Keeping in mind the acceptor and donor trap relative concentration requirement for achieving higher breakdown buffer, as depicted in part I of this paper, silicon carbon codoping of GaN buffer is proposed and explored in this paper. The proposed improvement in breakdown voltage is supported by physical insight into the avalanche phenomena and role of acceptor/donor traps. GaN buffer design parameters and their impact on breakdown voltage as well as leakage current are presented. Finally, a modified Si-doping profile in the GaN buffer is proposed to lower the C-doping concentration near GaN channel to mitigate the adverse effects of acceptor traps in GaN buffer. © 1963-2012 IEEE.

World University root node

IEEE Transactions on Electron Devices

Part II: Proposals to Independently Engineer Donor and Acceptor Trap Concentrations in GaN Buffer for Ultrahigh Breakdown AlGaN/GaN HEMTs

Effect of UV irradiation (λPeak = 365 nm) on the electrical performance of the OFETs with CuPc as active layer is demonstrated. The devices have shown stable electrical performance under dark with avg. and max. field effect mobility of ( 1.0 ± 0.3 ) × 10 -2 and 1.4 × 10-2 cm2, V-1, s-1 respectively. Under UV illumination there found a shift in threshold voltage and change in ON current along with fast response and recovery time of 0.4 s and 2 s respectively with periodic UV ON-OFF pulses. © 2019 IEEE.

2019 Electron Devices Technology and Manufacturing Conference, EDTM 2019

Copper (II) Phthalocyanine based Organic Field-Effect Transistors for UV Photo-detection

Due to increase in number of wireless devices for the development of smarter spaces such as offices, homes etc., Wi-Fi devices are available as off-the-shelf sensing devices. Researchers are looking for various sensing applications which can make reuse of already installed devices to make the human life easy. Wireless human sensing (WHS) has evolved as a field of study of interaction between the human body and on-going wireless communication to extract various human activities, such as sleep, without attaching any sensor to the body. Sleep is an important part of human life and a quality sleep is essential for healthy being. Due to various sleep disorders and physiological conditions quality sleep is obstructed. It is essential to monitor the sleep to estimate quality of the sleep so the remedial measures can be taken thereof. The movements viz. of limbs turns and rollovers made by the subject on the bed during the sleep can be observed with the proposed method of sleep monitoring and a corresponding movement score is created. This is for the first time when the sleep quality is being estimated on the basis of this score by using WHS. We present here optimistic prelim results of the sleep quality estimation based on rollovers through an Artificial Intelligence enabled Wi-Fi network. © 2019 IEEE.

International Symposium on Advanced Networks and Telecommunication Systems, ANTS

AI-enabled Wi-Fi Network to Estimate Human Sleep Quality based on Intensity of Movements

Here, we propose the construction of a sliding mode controller (SMC) for the fractional order descriptor (FOD) systems. This controller design mainly aims to stabilize the FOD system even in presence of matched disturbances by rejecting the disturbance. The controller is designed using an integral sliding mode (ISM) technique. Here, the control law is framed in such a way that it is at least continuous, by which it helps in eliminating the harmful chattering effects of the actuator and also meets the admissibility requirement related to control for the FOD systems. © 2019 EUCA.

2019 18th European Control Conference, ECC 2019

Integral sliding mode control for fractional order descriptor systems

We report a MoS2/GaN heterojunction-based gas sensor by depositing MoS2 over a GaN substrate via a highly controllable and scalable sputtering technique coupled with a post sulfurization process in a sulfur-rich environment. The microscopic and spectroscopic measurements expose the presence of highly crystalline and homogenous few atomic layer MoS2 on top of molecular beam epitaxially grown GaN film. Upon hydrogen exposure, the molecular adsorption tuned the barrier height at the MoS2/GaN interface under the reverse biased condition, thus resulting in high sensitivity. Our results reveal that temperature strongly affects the sensitivity of the device and it increases from 21% to 157% for 1% hydrogen with an increase in temperature (25-150 °C). For a deeper understanding of carrier dynamics at the heterointerface, we visualized the band alignment across the MoS2/GaN heterojunction having valence band and conduction band offset values of 1.75 and 0.28 eV. The sensing mechanism was demonstrated based on an energy band diagram at the MoS2/GaN interface in the presence and absence of hydrogen exposure. The proposed methodology can be readily applied to other combinations of heterostructures for sensing different gas analytes. © 2019 IOP Publishing Ltd.

Nanotechnology

A high-performance hydrogen sensor based on a reverse-biased MoS2/GaN heterojunction

Here, we demonstrate improved NO2 gas sensing properties based on reduced graphene oxide (rGO) decorated V2O5 thin film. Excluding the DC sputtering grown V2O5 thin film, rGO was spread over V2O5 thin film by the drop cast method. The formation of several p-n heterojunctions was greatly affected by the current-voltage relation of the rGO-decorated V2O5 thin film due to the p-type and n-type nature of rGO and V2O5, respectively. Initially with rGO decoration on V2O5 thin film, current decreased in comparison to the pristine V2O5 thin film, whereas depositing rGO film on a glass substrate drastically increased current. Among all sensors, only the rGO-decorated V2O5 sensor revealed a maximum NO2 gas sensing response for 100 ppm at 150 °C, and it achieved an approximately 61% higher response than the V2O5 sensor. The elaborate mechanism for an extremely high sensing response is attributed to the formation and modulation of p-n heterojunctions at the interface of rGO and V2O5. In addition, the presence of active sites like oxygenous functional groups on the rGO surface enhanced the sensing response. On that account, sensors based on rGO-decorated V2O5 thin film are highly suitable for the purpose of NO2 gas sensing. They enable the timely detection of the gas, further protecting the ecosystem from its harmful effects. © 2019 IOP Publishing Ltd.

NO2 gas sensing performance enhancement based on reduced graphene oxide decorated V2O5 thin films

MoO3 is a well-known multifunctional material which can be potentially used in a distinct gas-sensing applications. In this study, we grow the large-scale nanonetwork composed of α-MoO3 nanosheets by using conventional chemical vapor deposition method. The microscopic and spectroscopic characterizations confirm the continuity and crystallinity of the deposited MoO3 film. The dynamic response resistance of the device reveals a high sensitivity of 53% for 1% hydrogen at 180 °C. A detailed gas-sensing mechanism was explained by the depletion-layer modulation process. © 2019 IEEE.

2019 IEEE 5th International Conference for Convergence in Technology, I2CT 2019

Growth of Large-Scale α-MoO3 on SiO2 and Its Uses for Efficient Hydrogen Sensing Application

We demonstrate a highly sensitive and selective sensing platform for the electrochemical detection of Hg2+ in aqueous media. A graphene oxide (GO) and silver nanowire (AgNW) nanocomposites modified platinum (Pt) electrode has been applied to determine Hg2+ by using square-wave anodic stripping voltammetry (SWASV). The synergistic effect of graphene oxide and conductive AgNW greatly facilitates faster electron transport and sensing behavior for Hg2+. Under the optimum conditions, the sensor shows a high sensitivity of ∼0.29 μA/nM and a linear response in the range 1-70 nM toward Hg2+. The detection limit of the GO-AgNW nanocomposites modified electrode toward Hg2+ is ∼0.1 nM, which is significantly less than the safety limit defined by the World Health Organization. The sensor has an excellent selective response to Hg2+ against other interfering heavy metal ions such as Pb2+, Cd2+, Cu2+, Na+, and Ag+. In addition, the sensor exhibits a high repeatability and reproducibility. The sensor is employed for the detection of Hg2+ in tap water samples with an outstanding performance, suggesting it is a very promising platform for on-site monitoring of Hg2+ in water. Copyright © 2019 American Chemical Society.

ACS Applied Nano Materials

Graphene Oxide-Silver Nanowire Nanocomposites for Enhanced Sensing of Hg2+

This paper presents an analysis and estimation of timing error due to the power supply noise for a five-stage CMOS tapered buffer used in the clock distribution network for the application of successive approximation register (SAR). The complete design is simulated in standard 28 nm CMOS technology with the supply voltage of 0.9 V. The closed-form expressions for time interval error have been derived using the matrix inversion method, considering the impact of deterministic supply noise. The results obtained from a slope-based semianalytical jitter estimation method are compared with the SPICE based simulations. The results show a good agreement with a maximum error of 4 %. © 2019 The Institute of Electronics, Information and Communication Engineer.

2019 Joint International Symposium on Electromagnetic Compatibility, Sapporo and Asia-Pacific International Symposium on Electromagnetic Compatibility, EMC Sapporo/APEMC 2019

Jitter estimation in a CMOS tapered buffer for an application of clock distribution network

This paper presents an efficient method for the estimation of jitter due to power supply noise in a chain-of-inverters including the on-chip-interconnects. An analytical noise transfer function from power supply to output is derived based on a small-signal analysis. The estimation of jitter is done using a slope-based semi-analytical approach and the results are compared with the SPICE-based simulations. © 2019 IEEE.