Papers by Author: Marian Badila

Abstract: Two characterization methods are compared in terms of their suitability for predicting the electrical behavior of non-uniform Ni/4H-SiC Schottky contacts up to 450°C, using data measured at lower temperatures. These techniques are based on the established Gaussian distribution of barrier heights model and a recently proposed discrete barrier distribution model, respectively. Two samples with different degrees of contact inhomogeneity are measured and their forward characteristics are fitted using both techniques. The Gaussian distribution approach is shown to accurately fit experimental data only for the nearly-uniform sample, while requiring the extraction of two separate barrier height values from measurements in the room-250°C range, only. When attempting to use this method to characterize the sample with strong non-uniformity, fitting accuracy (given by R²) drops under 90%. In contrast, the discrete barrier distribution technique is proven able to forecast the electrical behavior of both samples (with R² > 99% in most cases), over the entire room-450°C range, using a single Schottky barrier for each device (1.61V, corresponding to a Ni₂Si Schottky contact and 0.9V, afferent to a Ni metallization).

Abstract: Different characterization techniques have been used in order to evaluate the electrical behavior of Pt/SiC-Schottky diodes and determine their capability as temperature sensors. I-V characteristics for fabricated devices were measured up to 400°C. Subsequent conventional parameter extraction evinced a barrier height increase with temperature, suggesting inhomogeneous contact formation. The energy activation method was carried out in order to identify both the effective barrier height for the devices and the non-uniformity parameter (p). Despite severe degrees of contact inhomogeneity, the diodes were found adequate for temperature sensing applications over the 26°C – 400°C range, with sensitivities up to 1.59 mV/°C.

Abstract: This paper proposes a method of characterizing silicon carbide Schottky diodes with inhomogeneous contacts in temperature sensing applications. Using the energy activation technique, temperature intervals where the effective barrier height is constant are determined. Unlike the conventional barrier which increases with temperature for inhomogeneous diodes, the effective barrier has physical meaning and can be used for sensor performance evaluation. The utility of effective barrier analysis is confirmed on fabricated Ni/4H-SiC Schottky diodes with different annealing conditions and different degrees of barrier non-uniformity. The good agreement between calculated and experimental data proves the suitable behavior of inhomogeneous diodes as sensors for different temperature ranges.

Abstract: A fully electrically isolated package for a SiC temperature sensor, able to work at high temperature, is presented in this paper. The adopted packaging solution was tested under thermal stress by varying the temperature between 300C and 400C (for 500 cycles) and between 50C and 400C (for other 500 cycles). The thermal stress had negligible effect on the capsules leakage currents (measured from the sensor terminals to the package metal casing) and did not degrade the glass which ensures the sealing of the capsule. The measurements and microphysical investigations showed a stable operation of the package up to temperatures of 400C.