Stannous selenide is a layered semiconductor with a puckered honeycomb lattice that constitutes a polar analogue of black phosphorus, and of great interest as a thermoelectric material [1-3]. Hole doped SnSe supports a large Seebeck coefficient at high conductivity. We combine experimental techniques in the form of angle resolved photo-emission spectroscopy, optical reflection spectroscopy and magnetotransport measurements to map out a multiple-valley valence band structure and a quasi two-dimensional dispersion. The quasi two-dimensional dispersion realizes the low-dimensional Hicks-Dresselhaus thermoelectric, which contributes to the high Seebeck coefficient reported at high carrier density [1-2]. We further demonstrate that the hole accumulation layer in exfoliated SnSe transistors exhibits a field effect mobility of up to 250 cm²/Vs at T=1.3 K. Unintentional hole doping and persistent photoconductivity has been observed, suggesting material quality can be further improved. SnSe is thus found to be a high quality, quasi two-dimensional semiconductor.

References:

[1] L.-D. Zhao et al., Nature 508, 373 (2014).

[2] L.-D. Zhao et al., Science 351, 141 (2016).

[3] C. W. Li et al., Nature Phys. 11, 1063 (2015).