  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$45%
incorporation of the incoming Ga flux), making MBE growth on this orientation
feasible. Moreover, through the employment of the investigated four different
(100) substrate offcuts along the [00-1] direction (i.e., 0$^\circ$, 2$^\circ$,
4$^\circ$, 6$^\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.
