Thermoelectric properties of GaN with carrier concentration modulation: an experimental and theoretical investigation

The present work investigates the less explored thermoelectric properties of the n-type GaN semiconductor by combining both experimental and computational tools. The Seebeck coefficients of GaN epitaxial thin films were experimentally measured in the wide temperature range from 77 K to 650 K in steps of similar to 10 K covering both low and high-temperature regimes as a function of the carrier concentration (2 x 10(16), 2 x 10(17), 4 x 10(17) and 8 x 10(17) cm(-3)). The measured Seebeck coefficient at room temperature was found to be highest (-374 mu V K-1) at the lowest concentration of 4 x 10(16) cm(-3), and decreases in magnitude monotonically (-327.6 mu V K-1, -295 mu V K-1, -246 mu V K-1 for 2 x 10(17), 4 x 10(17), 8 x 10(17) cm(-3), respectively) as the sample carrier concentration increases. The Seebeck coefficient remains negative in the entire temperature range under study indicating that electrons are the dominant carriers. To understand the temperature-dependent behaviour, we also carried out the electronic structure and transport coefficient calculations using the Tran-Blaha modified Becke-Johnson (TB-mBJ) potential and semiclassical Boltzmann transport theory implemented in WIEN2k and BoltzTraP code, respectively. The experimentally observed carrier concentrations were used in the calculations. The estimated results obtained under constant relaxation time approximations provide a very good agreement between the theoretical and experimental data of Seebeck coefficients in the temperature range from 260 to 625 K.

Automated summary

This study investigates the thermoelectric properties of n-type GaN semiconductor through experimental and computational tools, revealing that the Seebeck coefficient decreases with increasing carrier concentration, with electrons being the dominant carriers. The experimental results and theoretical calculations show good agreement in the temperature range of 260 to 625 K.