Homoepitaxial growth of β-Ga2O3 by MOVPE on vicinal (100) oriented substrates: Influence of growth parameters

Beta-gallium oxide (β-Ga2O3) is an emerging ultra-wide bandgap (4.8 eV) [1] semiconductor material. The high band gap leads to a theoretical breakdown field strength of 8 MV/cm [2], which enables the potential for β-Ga2O3 to outperform SiC and GaN and to become the next generation of high-performance material with respect to power electronic applications. Since transistors based on β-Ga2O3 benefit from a low on-resistance at a given breakdown voltage less power losses within a transistor switching operation can be achieved [3]. Thereby the electrically active part of the device is made up of a homoepitaxial thin layer. To fulfil the requirements from the device side, the epitaxial β-Ga2O3 layer has to have high crystalline perfections. To achieve such high quality layers was the aim of this work. β-Ga2O3 thin layer were grown homoepitaxially by MOVPE [4, 5] on Mg-doped β-Ga2O3 (100) substrates [6] with 2°, 4° and 6° miscut [7]. A development of the growth process with respect to growth modes and growth rate has been done. The Investigations were focusing on the interplay of the technical parameters i.e.: chamber pressure, Ar- push gas, precursor flux and their ratios. A transition from 2D island to step flow to step bunching growth modes has been achieved by varying the chamber pressure and/or the Ga/O2 ratio. This work shows that an adjusting of the effective diffusion length to the substrate step width is crucial to obtain step flow growth and with that high quality β-Ga2O3 (100) layers with electron mobilities above 150 cm²/Vs.