Localized Surface Doping Induced Ultralow Contact Resistance between Metal and (Bi,Sb)2Te3 Thermoelectric Films.

Abstract

Micro thermoelectric devices are expected to further improve the cooling density for the temperature control of electronic devices; nevertheless, the high contact resistivity between metals and semiconductors critically limits their applications, especially in chip cooling with extremely high heat flux. Herein, based on the calculated results, a low specific contact resistivity of ∼10-7 Ω cm2 at the interface is required to guarantee a desirable cooling power density of micro devices. Thus, we developed a generally applicable interfacial modulation strategy via localized surface doping of thermoelectric films, and the feasibility of such a doping approach for both n/p-type (Bi,Sb)2Te3 films was demonstrated, which can effectively increase the surface-majority carrier concentration explained by the charge transfer mechanism. With a proper doping level, ultralow specific contact resistivities at the interfaces are obtained for n-type (6.71 × 10-8 Ω cm2) and p-type (3.70 × 10-7 Ω cm2) (Bi,Sb)2Te3 layers, respectively, which is mainly attributed to the carrier tunneling enhancement with a narrowed interfacial contact barrier width. This work provides an effective scheme to further reduce the internal resistance of micro thermoelectric coolers, which can also be extended as a kind of universal interfacial modification technique for micro semiconductor devices.