Non-contact thermal conductivity measurements of p-doped and n-doped gold covered natural and isotopically-pure silicon and their oxides

The laser-based, non-contact, non-destructive transient thermo-reflectance (TTR) method was used to measure: (i) the thermal conductivity of natural silicon and isotopically-pure silicon-28 layers that are epitaxially grown on natural silicon substrates; (ii) the thermal conductivity of the oxide of natural and isotopically-pure silicon; and (iii) the influence of doping type and level on the thermal conductivity at room temperature (300 K). The third study was carried out for low and higher levels of both phosphorous (p-type) and boron (n-type) doping. The results reveal that the thermal conductivity of silicon-28 oxide is equal to 1.43 W/m-K and is similar to the thermal conductivity reported for the oxide of natural silicon, i.e., 1.4 W/m-K. The data also shows consistent differences (∼55%) in the thermal conductivity between natural and isotopically-pure Si, independently of the level of doping. Both the p and n-doping produce a decrease (∼18%) in the thermal conductivity for both natural and isotopically-pure silicon. The thermal interface resistance between the top gold layer and the underlying epitaxial layer has also been measured and found to vary slightly from sample to sample.