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

Homoepitaxial β-Ga2O3 layers grown via molecular beam epitaxy (MBE) have exhibited prohibitively low growth rates on (100) oriented substrates in the past. In this work, we investigate the possibility to employ indium-assisted metal exchange catalyzed (MEXCAT) MBE to overcome this limit. We demonstrate that the fine 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 the step-flow growth mechanism at relatively high growth rates for β-Ga2O3 homoepitaxy (i.e., around 1.5 nm/min, ≈ 45% incorporation of the incoming Ga flux), making MBE growth in this orientation feasible. Moreover, through the employment of the four investigated different (100) substrate offcuts along the [00-1] direction (i.e., 0°, 2°, 4°, and 6°), we give experimental evidence on the fundamental role of the (-201) step edges as nucleation sites in the growth of (100)-oriented Ga2O3 films by MBE.