Formation of various phases of gallium oxide films depending on substrate planes and deposition gases

Progress in Sputter Growth of β‐Ga2O3 by Applying Pulsed‐Mode Operation

“…In principle, α ‐phase Ga 2 O 3 shows a better lattice match with c ‐plane sapphire than its β ‐phase. However, β ‐phase Ga 2 O 3 is more commonly observed when growth occurs on this kind of substrate, presumably due to its lower chemical potential . Furthermore, surface roughness and defect density on the substrate surface affect the growth conditions and, thus, the crystallization of different phases .…”

“…However, β ‐phase Ga 2 O 3 is more commonly observed when growth occurs on this kind of substrate, presumably due to its lower chemical potential . Furthermore, surface roughness and defect density on the substrate surface affect the growth conditions and, thus, the crystallization of different phases . For example, a shift from β ‐phase to γ ‐phase was observed when growing in an environment containing water vapor, detrimental for the formation of high‐temperature phases .…”

“…Furthermore, surface roughness and defect density on the substrate surface affect the growth conditions and, thus, the crystallization of different phases . For example, a shift from β ‐phase to γ ‐phase was observed when growing in an environment containing water vapor, detrimental for the formation of high‐temperature phases . Thus, we expect the diffractogram to change significantly after carrying out postgrowth thermal treatment.…”

“…The temperature, the actual growth temperature (surface temperature), was expected to be considerably higher, depending on the RF power coupled into the plasma, the target‐substrate geometry, and the target's thermal conductivity. The temperature range was chosen in accordance with the findings of Akazawa and Zhang et al, who observed the threshold temperature of crystalline Ga 2 O 3 at 500 and 300 °C, respectively . Details on the distinct temperature characteristics of the setup can be found elsewhere …”

“…Therefore, an increase in the growth rate is often required to ensure use on an industrial scale. In those cases, sputtering techniques seem to be viable candidates for achieving this goal . Atoms ejected from the target's surface by energetic ion impingement are neutral unless they are ionized, inter alia, by application of very high power to the discharge .…”