Practical Contact Resistance Measurement Method for Bulk Bi₂Te₃-Based Thermoelectric Devices

Abstract

The impact of contact resistance on thermoelectric (TE) device performance grows more significant as devices are scaled down. To improve and understand the effects of contact resistance on bulk TE device performance, a reliable experimental measurement method is needed. There are many popular methods to extract contact resistance, but they are only well suited for measuring metal contacts on thin films and do not necessarily translate to measuring contact resistance on bulk TE materials. The authors present a measurement technique that precisely measures contact resistance on bulk TE materials by making and testing stacks of bulk, metal-coated TE wafers using TE industry-standard processes. An equation that uses the Z of the stacked device to extract the contact resistance is used to reduce the sensitivity to resistivity variations of the TE material. Another advantage of this technique is that it exploits realistic TE device manufacturing techniques and results in an almost device-like structure. The lowest contact resistivity measured was 1.1 × 10⁻⁶ Ω cm² and 1.3 × 10⁻⁶ Ω cm² for n- and p-type materials, respectively using a newly developed process at 300 K. The uncertainty in the contact resistivity values for each sample was 10% to 20%, which is quite good for measurements in the 10⁻⁶ Ω cm² range.