Thermal sensors based on delafossite film/p-silicon diode for low-temperature measurements

Abstract

A CuFeO2 film was prepared on p-type silicon wafer to fabricate an Al/CuFeO2/p-Si/Al diode by the sol–gel method. The temperature and frequency dependence of electrical characteristics of Al/CuFeO2/p-Si/Al diode were investigated using current–voltage (I–V) and capacitance/conductance–voltage (C/G–V) measurements. It is found that the ideality factor (n) decreases while zero-bias barrier height (Φ Bo) increases with increasing temperature. The conventional Richardson plot [ln(I o/T 2) vs. 1000/T] shows a linearity above about 200 °K. From the slope and intercept of the linear region, the values of activation energy (E a) and Richardson constant (A*) were found to be 0.15 eV and 1.24 × 10−8 A cm−2 K−2, respectively. Then, the values of mean barrier height and A* were determined from the modified Richardson plot [ln(I 0/T 2)−q 2 σ 0 2 /2k 2 T 2 vs. 1000/T] and found to be 1.06 eV and 33.87 A cm−2 K−2, respectively. The calculated A* value is very close to the theoretical value of 32 A cm−2 K−2 for p-type Si. The obtained results indicate that Al/CuFeO2/p-Si/Al diode can be used as a temperature measurement sensor for low-temperature controlling applications.