Offcut-related step-flow and growth rate enhancement during (100) $β$-Ga2O3 homoepitaxy by metal-exchange catalyzed molecular beam epitaxy (MEXCAT-MBE)

Abstract: In this work we investigate the growth of $\beta$-Ga2O3 homoepitaxial layers on top of (100) oriented substrates via indium-assisted metal exchange catalyzed molecular beam epitaxy (MEXCAT-MBE) which have exhibited prohibitively low growth rates by non-catalyzed MBE in the past. We demonstrate that the proper tuning of the MEXCAT growth parameters and the choice of a proper substrate offcut allow for the deposition of thin films with high structural quality via step-flow growth mechanism at relatively high growth rates for $\beta$-Ga2O3 homoepitaxy (i.e., around 1.5 nm/min, $\approx$45% incorporation of the incoming Ga flux), making MBE growth on this orientation feasible. Moreover, through the employment of the investigated four different (100) substrate offcuts along the [00-1] direction (i.e., 0$<sup>\circ$, 2$<sup>\circ$, 4$<sup>\circ$, 6$<sup>\circ$) we give experimental evidence on the fundamental role of the (-201) step edges as nucleation sites for growth of (100)-oriented Ga2O3 films by MBE.