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

A CuFeO 2 film was prepared on p-type silicon wafer to fabricate an Al/CuFeO 2 /p-Si/Al diode by the sol–gel method. The temperature and frequency dependence of electrical characteristics of Al/CuFeO 2 /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 /2 k 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/CuFeO 2 /p-Si/Al diode can be used as a temperature measurement sensor for low-temperature controlling applications.