Assessment of the structural and electronic properties of Ga[formula omitted]In[formula omitted]P semiconductors for betavoltaic energy conversion systems

Abstract

Indium gallium phosphide (GaxIn1−xP) semiconductors are attractive for betavoltaic batteries because of their excellent structural, thermophysical, and electronic properties. In the present work, we investigate the structural strength and electronic properties of zinc-blende GaxIn1−xP systems, for 0≤x≤1, using first-principles calculations. The most stable structures for different compositions are determined by a systematic evaluation of the atomic configurations. The dynamical stability of the structures is verified by examination of the phonon spectra. To assess the tolerance to radiation damage, we evaluated the minimum threshold displacement energy (Ed) for each atom type in the system. The Ed is estimated from simulations of recoil atom events using ab-initio molecular dynamics. We find a substantial effect of the composition on the electronic properties. In particular, the bandgap is relatively low for 0<x<0.5. The Ed was found to mainly depend on the crystallographic direction for In and P, whereas a considerable effect of the composition is observed for Ga. Overall, GaInP is found to be the more resistant to the radiation-induced degradation and the bandgap is also less affected by structural damage. Therefore, our results indicate that Ga0.25In0.75P is overall an excellent candidate for tritium-based betavoltaic batteries.