Quasi-two-dimensional thermoelectricity in SnSe

TL;DR

This study reveals that hole-doped SnSe has a quasi-two-dimensional valence band structure with high mobility, supporting high Seebeck coefficients at elevated conductivities, making it promising for thermoelectric applications.

Contribution

The paper uncovers the quasi-two-dimensional electronic structure of SnSe and demonstrates its high mobility and thermoelectric potential through experimental measurements.

Findings

SnSe exhibits a multiple-valley valence band structure.

SnSe supports high Seebeck coefficient at high carrier densities.

Hole accumulation layers in SnSe transistors show mobility up to 250 cm²/Vs.

Abstract

Stannous selenide is a layered semiconductor that is a polar analogue of black phosphorus, and of great interest as a thermoelectric material. Unusually, hole doped SnSe supports a large Seebeck coefficient at high conductivity, which has not been explained to date. Angle resolved photo-emission spectroscopy, optical reflection spectroscopy and magnetotransport measurements reveal a multiple-valley valence band structure and a quasi two-dimensional dispersion, realizing a Hicks-Dresselhaus thermoelectric contributing to the high Seebeck coefficient at high carrier density. We further demonstrate that the hole accumulation layer in exfoliated SnSe transistors exhibits a field effect mobility of up to $250~\mathrm{cm^2/Vs}$ at $T=1.3~\mathrm{K}$. SnSe is thus found to be a high quality, quasi two-dimensional semiconductor ideal for thermoelectric applications.