Review of SiGe Alloys: Latest Research Progress and Optimization Strategies for Thermoelectric Properties

Silicon-germanium (SiGe) alloy, as a representative medium and high temperature thermoelectric material, has been widely applied in auxiliary power supply of space exploration spacecraft. SiGe alloy has significant advantages such as stable structure, rich elements, non-toxic, high-temperature resistance, and easy industrial integration. However, the lower thermoelectric performance limits the practical application and promotion of SiGe alloys. Based on above, this article comprehensively describes the collaborative optimization strategies of SiGe alloys in both electrical and thermal properties, as well as relevant latest research progress. In terms of electrical properties, the importance of modulation doping and energy filtering mechanism to improve the power factor of SiGe alloys was revealed; In terms of thermal properties, a detailed review was conducted on the strategies for reducing lattice thermal conductivity of SiGe alloys, including nanostructure, SiGe-metal silicide/silicide composite, and SiGe-oxide composite strategies. And the effects of different optimization strategies on reducing lattice thermal conductivity were compared. Through collaborative optimization of electrical and thermal transport parameters, the zT values of p-type and n-type SiGe-based thermoelectric materials reached 1.81 (1100 K) and 1.7 (1173 K), respectively, which are the highest values reported in current research. This article provides a certain reference for further optimization of the thermoelectric properties of SiGe bulk materials.