T. Kifle

Bio: T. Kifle is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Grain boundary diffusion coefficient & Polysilicon depletion effect. The author has an hindex of 1, co-authored 1 publications receiving 51 citations.

Physical Model for the Resistivity and Temperature Coefficient of Resistivity in Heavily Doped Polysilicon

Abstract: One of the key benefits of using polysilicon as the material for resistors and piezoresistors is that the temperature coefficient of resistivity (TCR) can be tailored to be negative, zero, or positive by adjusting the doping concentration. This paper focuses on optimization of the boron doping of low-pressure chemical vapor deposited polysilicon resistors for obtaining near-zero TCR and development of a physical model that explains quantitatively all the results obtained in the optimization experiments encompassing the doping concentration ranges that show negative, near-zero, and positive TCR values in the polysilicon resistors. The proposed model considers single-crystal silicon grain in equilibrium with amorphous silicon grain boundary. The grain boundary carrier concentration is calculated considering exponential band tails in the density of states for amorphous silicon in the grain boundaries. Comparison of the results from the model shows excellent agreement with the measured values of resistivity as well as TCR for heavily doped polysilicon. It is shown that the trap density for holes in the grain boundary increases as the square root of the doping concentration, which is consistent with the defect compensation model of doping in the amorphous silicon grain boundaries

Thermoresistive Effect for Advanced Thermal Sensors: Fundamentals, Design Considerations, and Applications

Abstract: Microelectromechanical systems sensors have been intensively developed utilizing various physical concepts, such as piezoresistive, piezoelectric, and thermoresistive effects. Among these sensing concepts, the thermoresistive effect is of interest for a wide range of thermal sensors and devices, thanks to its simplicity in implementation and high sensitivity. The effect of temperature on the electrical resistance of some metals and semiconductors has been thoroughly investigated, leading to the significant growth and successful demonstration of thermal-based sensors, such as temperature sensors, convective accelerometers and gyroscopes, and thermal flow sensors. In this paper, we review the fundamentals of the thermoresistive effect in metals and semiconductors. We also discuss the influence of design and fabrication parameters on the thermoresistive sensitivity. This paper includes several desirable features of thermoresistive sensors and recent developments in these sensors are summarized. This review provides insights into how it is affected by various parameters, and useful guidance for industrial designers in terms of high sensitivity and linearity and fast response. [2017-0022]

Real-Time Measurement of Temperature Sensitive Electrical Parameters in SiC Power MOSFETs

Abstract: This paper examines a number of techniques for junction temperature estimation of silicon carbide (SiC) MOSFET s devices based on the measurement of temperature sensitive electrical parameters for use in online condition monitoring. Linearity, sensitivity to temperature, and circuit design for practical implementation are discussed in detail. A demonstrator based on the measurement of the quasi-threshold voltage, the turn- on transient characteristic ( $di/ dt$ ), the on -state voltage, and the gate current peak is designed and validated. It is shown that the threshold voltage, the estimation of the gate current peak, and the on -state voltage have potentially good sensitivity to temperature variation and linearity over a wide operating range. Very low sensitivity to temperature is shown for $di/ dt$ . The proposed method can provide a valuable tool for continuous health monitoring in emerging applications of SiC devices to high-reliability applications.

Graphite on paper as material for sensitive thermoresistive sensors

Abstract: This paper reports on the thermoresistive properties of graphite on paper (GOP). A negative temperature coefficient of resistance (TCR) from −2900 to −4400 ppm K−1 was observed for the GOP. This negative and large TCR is attributed to an increase in the thermionic emission current over a low potential barrier with increasing temperature. The potential barrier was found to be 33 meV between the graphite grains. The paper also demonstrates the use of the GOP in a highly sensitive (0.83 mV (m s−1)−0.8 mW−1) GOP-based anemometer, indicating strong feasibility of using this material for low-cost and sensitive thermal sensing applications.

Silicon Micromachined Pressure Sensors

Abstract: Silicon micromachining for realizing micro mechanical structures has received considerable interest due to the several advantages of this technology over the conventional machining techniques. Silicon pressure sensors were the first micro mechanical transducers developed. Since then the market for micromachined pressure sensors has grown in leaps and bounds and found application in all walks of life including defense and space applications. The relevant micromachining technology and the design considerations are reviewed in this paper. The paper also gives the latest developments in this area and gives the details of the polysilicon piezoresistor based pressure sensors with Silicon On Insulator (SOI) approach for integrating pressure sensor and associated electronics.