Engineering Electronic and Magnetic Properties of $(A_{x}Ga_{1-x})_{2}O_{3}$ [A=In or Tl] Alloys

Bandgap engineering aims at creating and controlling electronic states that can support specific technological applications. An example of bandgap engineering is the doping of $\beta$-$Ga_{2}O_{3}$ ($E_{g}$$\sim$4.8 eV), a wide gap insulator, that enables applications in UV sensing and in advanced power electronics. In this contribution, we use a Hubbard-U modified version of density-functional-theory (DFT) to study electronic effects of In and Tl dopants as well as vacancies on material properties of $\beta$-$Ga_{2}O_{3}$. We compare and contrast the electronic properties of little studied $(Tl_{x}Ga_{1-x})_{2}O_{3}$ with those of the much better characterized $(In_{x}Ga_{1-x})_{2}O_{3}$ alloys. Our calculations show that Tl-doping requires $\sim$4 times less doping to transverse the complete UV range as compared to In-doping, while showing comparable thermodynamic behavior. Spin-polarized calculations show that tetrahedral and octahedral Ga vacancies lead to spin-polarized ground states in both doped and undoped $\beta$-$Ga_{2}O_{3}$. Thus, $(Tl_{x}Ga_{1-x})_{2}O_{3}$ may not only be of interest for optoelectronics but also as a materials platform for spintronics applications