Ti alloyed $\alpha$-Ga$_2$O$_3$: route towards wide band gap engineering

TL;DR

This study demonstrates that Ti can be used to effectively modify the band gap of $eta$-Ga$_2$O$_3$ by creating crystalline Ti:Ga$_2$O$_3$ films with tunable optical properties, advancing wide band gap engineering.

Contribution

It introduces a method to incorporate Ti into $eta$-Ga$_2$O$_3$ to achieve controlled band gap tuning while maintaining crystallinity at low Ti concentrations.

Findings

Crystalline Ti:Ga$_2$O$_3$ films with up to 5.3% Ti were synthesized.

Band gap modification of approximately 270 meV was achieved.

Maximum band gap change of ~1.1 eV observed at 61% Ti concentration.

Abstract

The suitability of Ti as a band gap modifier for $\alpha$-Ga$_2$O$_3$ was investigated, taking advantage of the isostructural {\alpha}-phases and high band gap difference between Ti$_2$O$_3$ and Ga$_2$O$_3$. Films of Ti:Ga$_2$O$_3$, with a range of Ti concentrations, synthesized by atomic layer deposition on sapphire substrates, were characterized to determine how crystallinity and band gap vary with composition for this alloy. The deposition of crystalline $\alpha$-(Ti$_x$Ga$_{1-x}$)$_2$O$_3$ films with up to x~5.3%, was demonstrated. At greater Ti concentration, the films became amorphous. Modification of the band gap over a range of ~ 270 meV was achieved across the crystalline films and a maximum change in band gap from pure $\alpha$-Ga$_2$O$_3$ of ~1.1 eV was observed for the films of greatest Ti fraction (61% Ti relative to Ga). The ability to maintain a crystalline phase at low fractions of Ti, accompanied by a significant modification in band gap shows promise for band gap engineering and the enhancement in versatility of application of $\alpha$-Ga$_2$O$_3$ in optoelectronic devices.