  Recent research in ultrawide-bandgap (UWBG) semiconductors has focused on
traditional materials such as Ga2O3, AlGaN, AlN, cubic BN, and diamond; however
some materials exhibiting single perovskite structure have been known to yield
bandgaps above 3.4 eV, such as BaZrO3. In this work we propose two novel
materials to be added to the family of UWBG semiconductors: Ba2CaTeO6
exhibiting a double perovskite structure and Ba2K2Te2O9 with a triple
perovskite structure. Using first principles hybrid functional calculations we
predict the bandgaps of all the studied systems to be above 4.5 eV with strong
optical absorption in the ultraviolet region. Furthermore, we show that holes
have a tendency to get trapped through lattice distortions in the vicinity of
oxygen atoms with average trapping energy of 0.25 eV,potentially preventing the
enhancement of p-type conductivity through traditional chemical doping.
