Widely tunable band gap in a multivalley semiconductor SnSe by potassium doping

TL;DR

This paper demonstrates that potassium doping can significantly tune the band gap of SnSe from 1.2 eV to 0.4 eV, revealing detailed electronic structures and enabling potential applications in tunable devices.

Contribution

It provides the first detailed electronic structure analysis of SnSe with both valence and conduction bands, and shows how potassium doping can widely tune its band gap.

Findings

SnSe has multivalley valence bands with large effective mass.

Potassium doping reveals single-valley conduction bands.

Band gap can be tuned from 1.2 eV to 0.4 eV through doping.

Abstract

SnSe, a group IV-VI monochalcogenide with layered crystal structure similar to black phosphorus, has recently attracted extensive interests due to its excellent thermoelectric properties and potential device applications. Experimental electronic structure of both the valence and conduction bands is critical for understanding the effects of hole versus electron doping on the thermoelectric properties, and to further reveal possible change of the band gap upon doping. Here, we report the multivalley valence bands with a large effective mass on semiconducting SnSe crystals and reveal single-valley conduction bands through electron doping to provide a complete picture of the thermoelectric physics. Moreover, by electron doping through potassium deposition, the band gap of SnSe can be widely tuned from 1.2 eV to 0.4 eV, providing new opportunities for tunable electronic and optoelectronic devices.