Ab initio Energetics and Thermoelectric Profiles of Gallium Pnictide Polytypes

Trupti K Gajaria,Prafulla K Jha,Shweta D Dabhi

doi:10.1038/s41598-019-41982-9

Trupti K Gajaria, Prafulla K Jha + Show 1 more

Open Access

https://doi.org/10.1038/s41598-019-41982-9

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Abstract

The state-of-the-art Density Functional Theory (DFT) is utilized to investigate the structural, electronic, vibrational, thermal and thermoelectric properties of gallium pnictides GaX (X = P, As, Sb) in cubic zincblende (ZB) and hexagonal wurtzite (WZ) phases. The lattice parameters, bulk modulus, energy band nature and bandgap values, phonon, thermal and thermoelectric properties are revisited for ZB phase while for WZ phase they are predictive. Our results agree reasonably well with the experimental and theoretical data wherever they are available. The phonon dispersion curves are computed to validate the dynamic stability of these two polytypes and for further investigating the thermal and thermoelectric properties. Our computed thermoelectric figure of merit ZT gives consistent results with highest observed magnitude of 0.72 and 0.56 for GaSb compound in ZB and WZ phases respectively. The first time calculated temperature variation of lattice thermal conductivity for WZ phase shows lower value than ZB phase and hence an important factor to enhance the figure of merit of considered gallium pnictides in WZ phase. Present results validate the importance of GaX in high temperature thermoelectric applications as the figure of merit ZT shows enhancement with significant reduction in thermal conductivity at higher temperature values.

Highlights

The thermoelectric studies on variety of semiconductors including III-V compounds[8,9,42,43,44,45,46,47,48,49,50] have gained greater attention due to the importance of thermal management in devices especially when, the device sizes are continuously decreasing
The lattice constants computed for GaP, GaAs and GaSb in ZB and WZ phases presented in Table 1 are slightly underestimated (1.2–2%) compared to the reported experimental values[18,19,20]
In a nut-shell, our results indicate GaSb compound to be more efficient for thermoelectric applications with overall figure of merit ZT, 0.72 and 0.56 in ZB and WZ phases respectively at 1200 K

Summary

Introduction

The thermoelectric studies on variety of semiconductors including III-V compounds[8,9,42,43,44,45,46,47,48,49,50] have gained greater attention due to the importance of thermal management in devices especially when, the device sizes are continuously decreasing. Literature survey reveals many theoretical reports on lattice conductivity computation for III-V compounds and alloys taking into consideration various aspects/parameters affecting it[8,44,46,51,52,53]. The signature contributions of III-V compounds in various cutting-edge technologies and urge to get more insight to their phase dependent properties, we have focused this study on the two polytypic phases; zincblende (ZB) and wurtzite (WZ), of gallium pnictides GaX (X = P, As, Sb) for investigating the structural, electronic, vibrational, thermal and thermoelectric properties. To validate the consistency of our ab initio calculations and support our results, we are revisiting the electronic and vibrational properties of GaX compounds for both phases

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