Thermopower modulation clarification of the intrinsic effective mass in a transparent oxide semiconductor, BaSnO3

TL;DR

This study accurately determined the intrinsic effective mass of BaSnO3 using thermopower modulation, clarifying previous scattered reports and identifying the threshold between degenerate and non-degenerate regimes for this transparent oxide semiconductor.

Contribution

We established the intrinsic effective mass of BaSnO3 as 0.40 m0 using thermopower modulation, providing clarity on its electronic properties and carrier mobility behavior.

Findings

Intrinsic effective mass of BaSnO3 is 0.40 m0.

Threshold of degenerate/non-degenerate behavior identified at 240 μV/K thermopower.

High mobility observed when Fermi level is above conduction band bottom.

Abstract

Although there are so many reports on the carrier effective mass (m*) of a transparent oxide semiconductor BaSnO3, it is almost impossible to know the intrinsic m* value because the reported m* values are scattered from 0.06 to 3.7 m0. Here we successfully clarified the intrinsic m* of BaSnO3, m*=0.40 0.01 m0, by the thermopower modulation clarification method. We also found the threshold of degenerate/non-degenerate semiconductor of BaSnO3; At the threshold, the thermopower value of both La-doped BaSnO3 and BaSnO3 TFT structure was 240 microvolt k-1, bulk carrier concentration was 1.4E19 cm-3, and two-dimensional sheet carrier concentration was 1.8E12 cm-2. When the EF locates above the parabolic shaped conduction band bottom, rather high mobility was observed. On the contrary, very low carrier mobility was observed when the EF lays below the threshold, most likely due to that the tail states suppress the carrier mobility. The present results are useful for further development of BaSnO3 based oxide electronics.