Sn-Induced Phase Stabilization and Enhanced Thermal Stability of κ-Ga(2)O(3) Grown by Mist Chemical Vapor Deposition

[Image: see text] Tin (Sn)-doped orthorhombic gallium oxide (κ-Ga(2)O(3)) films were grown on (0001) sapphire by mist chemical vapor deposition. It is known that κ-Ga(2)O(3) is more stable than α-Ga(2)O(3) (corundum) but less stable than β-Ga(2)O(3) (monoclinic). This thermodynamic stability means an optimal growth temperature (T(g)) of the κ-phase (600–650 °C) is also in between the two. At first, it was observed that Sn doping induced the κ-phase during the growth of the β-phase (T(g) = 700 °C). Interestingly, Sn could also promote the κ-phase even under the growth condition that strongly favors the α-phase (T(g) = 450 °C). The postgrowth annealing tests at 800–1000 °C showed that the thermal stability of the κ-phase depends on the Sn concentration. The higher the Sn concentration, the more stable the phase. The one with the highest Sn content showed no phase transition from κ to β after annealing at 800, 900, and 1000 °C for 30 min each. This enhancement of thermal stability promises more reliable high-power and high-frequency devices for which κ-Ga(2)O(3) is suitable. Although there was no correlation between Sn-induced phase stabilization and the crystal quality, cathodoluminescence revealed that increasing Sn concentration led to the strong suppression of the radiative recombination at 340 nm from the vacancy-related donor–acceptor pairs. This observation suggests that the phase stabilization by Sn could be related to a specific Ga site Sn replaces in the orthorhombic structure.