A highly stable temperature sensor based on Au/Cu/n-Si Schottky barrier diodes dependent on the inner metal thickness

Abstract

We have fabricated Au/n-Si (D1), Au/Cu/n-Si (D2), Au/Cu(4 nm)/n-Si (D3) and Au/Cu(2 nm)/n-Si (D4) Schottky barrier diodes (SBDs). The thickness of the Cu Schottky contact (SC) films for diodes D2, D3 and D4 was chosen as 100, 4 and 2 nm, respectively. We investigated the thermal sensitivity from the voltage-temperature (V-T) characteristics of the SBDs at different current levels. The V-T measurements were done in the temperature range from 10 to 320 K with steps of 2 K at different current levels from 50 nA to 141.70 mu A. The V-T curves showed a good degree of linearity for all SBDs. The slope dV/dT = alpha (alpha is the thermal sensitivity coefficient) for each diode decreased with increasing current from 50 nA to 141.70 mu A. However, the SBDs with a Cu SC had approximately the same alpha value independent of metal thickness at the same current level. That is, the value of the thermal sensitivity coefficient changed from approximately 2.48 mV K-1 at 50 nA to 1.82 at 141.70 mu A for the SBDs with a Cu SC independent of metal thickness. Furthermore, the alpha versus current level plots of the diodes exhibited a linear behavior. The intercept alpha (0) and slope d alpha /dI values of the alpha versus current level plots were obtained as 2.80 mV K-1 and -0.0843 mV A(-1) K-1 for D2, and 2.85 mV K-1 and -0.092 mV A(-1) K-1 for D3 and 2.83 mV K-1 and -0.0876 mV A(-1) K-1 for D4. These values are very close to each other and the difference between the slope (d alpha /dI) values is small enough to be neglected.