Disorder-Induced Ordering in Gallium Oxide Polymorphs

Abstract

Polymorphs are common in nature and can be stabilized by applying external pressure in materials. The pressure and strain can also be induced by the gradually accumulated radiation disorder. However, in semiconductors, the radiation disorder accumulation typically results in the amorphization instead of engaging polymorphism. By studying these phenomena in gallium oxide we found that the amorphization may be prominently suppressed by the monoclinic to orthorhombic phase transition. Utilizing this discovery, a highly oriented single-phase orthorhombic film on the top of the monoclinic gallium oxide substrate was fabricated. Exploring this system, a novel mode of the lateral polymorphic regrowth, not previously observed in solids, was detected. In combination, these data envisage a new direction of research on polymorphs in Ga 2 O 3 and, potentially, for similar polymorphic families in other materials.

Activation energy of silicon diffusion in gallium oxide: Roles of the mediating defects charge states and phase modification

“…Importantly, the change in the conditions for the VGa generation at the surface may be potentially induced not only by different atmospheres, but also by modifying the surface. Indeed, recently, ion-beam-induced phase transformations of -Ga2O3 to phase were reported [15,22]. In particular, Azarov et al [15] have demonstrated that a certain threshold in the density of the radiation damage may be reached to enable the to- phase transformation.…”

“…Indeed, recently, ion-beam-induced phase transformations of -Ga2O3 to phase were reported [15,22]. In particular, Azarov et al [15] have demonstrated that a certain threshold in the density of the radiation damage may be reached to enable the to- phase transformation. In relation to the present Si diffusion study, the conditions for the Si implants (as shown in Fig.…”

“…In relation to the present Si diffusion study, the conditions for the Si implants (as shown in Fig. 1) were selected to be under this threshold as compared with the heavier ion mass Ni, Ga, Ge, or Au implants, known to result into the -to- phase transformation in the near surface volume [15,22]. In the present work, in order to modify the Si diffusion conditions we fabricated pre-existing -phase surface layer on the top of the bulk -Ga2O3 wafer where Si diffused.…”

“…keV 58 Ni + ions to 2×10 14 cm -2 in order to form a pre-existing phase-modified layer in the region between 1 MeV Si implantation peak and the sample surface [15]. All implants were performed at room temperature, maintaining 7° off-angle orientation from a normal direction to minimize the channeling.…”

“…Selected samples were analyzed with 2theta X-ray diffraction (XRD) measurements using the Bruker AXS D8 Discover diffractometer with Cu Kα1 radiation in the locked-coupled mode. The XRD measurements were performed in order to check the phase status of the implanted samples in the context of the possible ion-beaminduced phase transformations [15]. Notably, the Si implants were insufficient to induce the phase transformation due to the lighter ion mass, enabling interesting comparison with Ni+Si implants characterized with the pre-existing phase modified surface layer.…”