Diameter dependent thermal sensitivity variation trend in Ni/4H-SiC Schottky diode temperature sensors

Abstract

This report is on the diameter dependent thermal sensitivity variation trend of Ni/4H-nSiC Schottky barrier diode (SBD) temperature sensors. Scaled SBDs of 2, 1.6, and 1.2 mm in diameter were fabricated using standard photolithography process comprising a field plate and a guard ring as edge terminations on the same epitaxial wafer. Taking into consideration the heat loss and power consumption, the thermal sensitivities of the fabricated SBDs were measured in the current range from 1 μA to 50 pA. The temperature was varied from 273 to 473 K in step of 25 K. An authoritative consequence of the present study is the observed increase in thermal sensitivity with the diameter of the fabricated SBDs. An exhaustive investigation confirms that in all diodes, there exist nanosized patches, which assumed to have different barrier heights and hence ascertained to be the main cause of anomalies in thermal sensitivity variation with diode size. Taking into account the effective area of these patches, theoretically fitted I–V curves to experimental data show that the numbers of patches were higher in diode with least size and decrease with the increase in the size of the diode. The corresponding barrier heights of these patches were found to be distributed in a Gaussian like manner at the fabricated Ni/4H-nSiC interface with least standard deviation (σ0) in the diode of maximum size.