Thermodynamic-kinetic competitive growth and interface physics of β-Ga2O3 thin films on fused quartz for deep ultraviolet detection

We report the growth of highly (400)-oriented β-Ga2O3 thin films on amorphous fused quartz at 600 °C via high-power impulse magnetron sputtering. To elucidate the non-epitaxial crystallization mechanism, we propose a thermodynamic-kinetic competitive growth model. Cross-sectional transmission electron microscopy and x-ray diffraction analyses reveal a spatially graded competition: near the film–substrate interface, energetic ion bombardment activates surface relaxation pathways that may effectively reduce the (2¯01) surface energy toward values comparable to those of the (100) family, potentially permitting the concurrent nucleation of (2¯01) and (200) seeds. As the film thickens, kinetically driven evolutionary selection progressively promotes the fast-growing (400) orientation to dominate the bulk, as evidenced by stable area ratios and an invariant (400) full width at half maximum across duty cycles. Integrating these oriented films into optoelectronic devices, we evaluate metal–semiconductor–metal deep-ultraviolet photodetectors to investigate interfacial contact physics. The Ti/Al bilayer electrode exhibits Ohmic-like transport attributed to thermodynamically driven interfacial reduction, while the pure Al electrode yields Schottky-like behavior, attributed to the intrinsic formation of a resistive Al2O3 layer. The Ti/Al device delivers a fourfold steeper photocurrent decay and enhanced spectral responsivity, demonstrating that Ohmic contact engineering facilitates carrier collection efficiency. These findings establish an integrated framework connecting competitive crystallization dynamics and contact thermodynamics for cost-effective β-Ga2O3 optoelectronics.