Thermoelectric cross-plane properties on p- and n-Ge/SixGe1-x superlattices

Ferre Llin, L., Samarelli, A., Cecchi, S., Chrastina, D., Isella, G., Müller Gubler, E., Etzelstorfer, T., Stangl, J. and Paul, D.J. (2016) Thermoelectric cross-plane properties on p- and n-Ge/SixGe1-x superlattices. Thin Solid Films, 602, pp. 90-94. (doi: 10.1016/j.tsf.2015.09.059)

Abstract

Silicon and germanium materials have demonstrated an increasing attraction for energy harvesting, due to their sustainability and integrability with complementary metal oxide semiconductor and micro-electro-mechanical-system technology. The thermoelectric efficiencies for these materials, however, are very poor at room temperature and so it is necessary to engineer them in order to compete with telluride based materials, which have demonstrated at room temperature the highest performances in literature [1]. Micro-fabricated devices consisting of mesa structures with integrated heaters, thermometers and Ohmic contacts were used to extract the cross-plane values of the Seebeck coefficient and the thermal conductivity from p- and n-Ge/SixGe1-x superlattices. A second device consisting in a modified circular transfer line method structure was used to extract the electrical conductivity of the materials. A range of p-Ge/Si0.5Ge0.5 superlattices with different doping levels was investigated in detail to determine the role of the doping density in dictating the thermoelectric properties. A second set of n-Ge/Si0.3Ge0.7 superlattices was fabricated to study the impact that quantum well thickness might have on the two thermoelectric figures of merit, and also to demonstrate a further reduction of the thermal conductivity by scattering phonons at different wavelengths. This technique has demonstrated to lower the thermal conductivity by a 25% by adding different barrier thicknesses per period.

• Item Type: Articles
• Additional Information: The authors would like to thank the EC ICT FET Proactive Initiative Towards Zeropower ICT for funding the research through the GREEN Silicon Project (No. 257750).
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Ferre Llin, Dr Lourdes and Samarelli, Mr Antonio and Paul, Professor Douglas
• Authors: Ferre Llin, L., Samarelli, A., Cecchi, S., Chrastina, D., Isella, G., Müller Gubler, E., Etzelstorfer, T., Stangl, J., and Paul, D.J.
• College/School: College of Science and Engineering > School of Engineering; College of Science and Engineering > School of Engineering > Electronics and Nanoscale Engineering
• Journal Name: Thin Solid Films
• Publisher: Elsevier
• ISSN: 0040-6090
• ISSN (Online): 1879-2731
• Published Online: 09 October 2015