Wide range temperature-dependent (80-630 K) study of Hall effect and the Seebeck coefficient of \b{eta}-Ga2O3 single crystals

TL;DR

This study measures the Seebeck coefficient and Hall effect of eta-Ga2O3 single crystals across 80-630 K, revealing electron dominance, impurity-related conduction, and thermoelectric properties relevant for high-power applications.

Contribution

It provides the first wide-temperature-range Seebeck coefficient data for Sn-doped eta-Ga2O3, linking transport mechanisms with structural and phonon characteristics.

Findings

Electrons are the dominant carriers across the entire temperature range.

Seebeck coefficient shows a non-monotonic trend with large negative values.

The figure-of-merit at 300 K is approximately 0.01.

Abstract

Investigation of Seebeck coefficient in ultra-wide bandgap materials presents a challenge in measurement, nevertheless, it is essential for understanding fundamental transport mechanisms involved in electrical and thermal conduction. \b{eta}-Ga2O3 is a strategic material for high power optoelectronic applications. Present work reports Seebeck coefficient measurement for single crystal Sn doped \b{eta}-Ga2O3 in a wide temperature range (80-630 K). The non-monotonic trend with large magnitude and negative sign in the entire temperature range shows electrons are dominant carriers. The structural and Raman characterization confirms the single-phase and presence of low, mid, and high-frequency phonon modes, respectively. Temperature dependent (90-350 K) Hall effect measurement was carried out as supplementary study. Hall mobility showed T1.12 for T less than 135 K and T-0.70 for T more than 220 K. Activation energies from Seebeck coefficient and conductivity analysis revealed presence of inter band conduction due to impurity defects. The room temperature Seebeck coefficient, power factor and thermal conductivity were found as 68.57 microV/K, 0.15 microW/K2cm and 14.2 W/mK, respectively. The value of the figure-of-merit for \b{eta}-Ga2O3 was found to be aprox. 0.01 (300 K).