Ion Rusu

An industrial temperature probe based on SiC diodes

A temperature probe based on 4H-SiC Schottky diodes is proposed. These diodes have been fabricated and characterized for temperature sensor applications. A conversion circuit to 4–20mA output current for ambient to maximum (400°C) input temperature was designed and tested.

High temperature sensor based on SiC Schottky diodes with undoped oxide ramp termination

A simple technology of 4H-SiC Schottky diode with oxide ramp termination is presented. The ramp is controlled by two undoped layers: an annealed (compact) oxide layer and as deposited layer, respectively.

Electrical Characterization of Ni-Silicide Schottky Contacts on SiC for High Performance Temperature Sensor

The electrical behavior and stability of a temperature sensor based on 4H-SiC Schottky diodes using Ni2Si as Schottky contact, are investigated. The ideality factor and the barrier height were found to be strongly dependent on the post-annealing temperature of the Ni contact (which lead to the formation of Ni2Si). A nearly ideal Schottky device, with the barrier height approaching the high value of 1.7eV, and a slight temperature dependence, was obtained after an annealing at TA=800°C. This high barrier height proves that Ni2Si is suitable as Schottky contact for temperature sensors, able to reliably operate up to 450°C. Sensor sensitivity levels between 1.00mV/°C and 2.70 mV/°C have been achieved.

High Temperature Hydrogen Sensor Based on Silicon Carbide (SiC) MOS Capacitor Structure

MOS capacitor devices based on silicon carbide (SiC) are largely used as hydrogen detectors in high temperature and chemically reactive environments. A SiC MOS capacitor structure used as hydrogen sensor is analyzed by extensive simulations. The sensitivity to hydrogen detection, stability to temperature variation and dependence on interface states concentration are evaluated. The effects of structure parameters on sensors performance are also investigated. Results show that the oxide layer type and thickness and the SiC polytype have a significant influence on the detectors performance. The proposed optimum structure for high temperature hydrogen detection is based on 3C-SiC substrate and 10nm TiO2 layer. In accordance with the simulations results, three types of masks are designed for the fabrication of SiC MOS capacitor structures.

High temperature characterization system for silicon carbide devices

In this paper it is described a design technique used to collect and analyse power devices characteristics in high temperatures domain. Following this technique, a complete hardware and software platform is built for thermal characterization of power devices.

A Fully Electrically Isolated Package for High Temperature SiC Sensors

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.

High Temperature SiC Sensor with an Isolated Package

This paper presents an improved version and new results on a temperature sensor based on SiC Schottky Barrier Diode (SBD). SiC SBD structures of different areas were packaged in a metallic-glass case. The encapsulated sensor was electrically measured at several temperatures. A good linearity of the forward voltage measured at a constant current versus temperature dependence was obtained in the temperature range of 150-400°C where the sensor is meant to operate. Optical investigation, correlated with electrical measurements, prove the reliability of the sensor structure and of the package solutions at temperatures up to 400°C.

Smart sensor for chemical compounds concentration

A Smart Sensor used for measuring the concentration of chemical compounds in fluids/solutions is designed, implemented and tested. The sensor comprises a potentiostat employed for three-electrode electrochemical cell (biosensor) biasing, a transimpedance amplifier and a digital interfacing system. The stability of the potentiostat and the linearity of the transimpedance amplifier are theoretically and experimentally investigated. Finally, the high performances of the smart sensor are demonstrated by simulations and measurements.

Barrier stability of Pt/4H-SiC Schottky diodes used for high temperature sensing

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.

Complete analytical submicron MOS transistor model for analogue applications

A compact analytical model of nanoscale MOS transistors which takes into account the effects of velocity saturation and channel length modulation is proven. Equations for the transfer and output characteristics and for the dynamic analogue parameters (transconductance and output resistance) are obtained, in the case of pMOS, as well as nMOS transistors. Experimental transfer and output characteristics of short channel devices match well with calculated curves based on the model, for different transistor geometries. A very good agreement of the new model with the experimental data for transconductance and output resistance is also obtained.