“…6 In the last years, several high permittivity oxides (Al 2 O 3 , HfO 2 , Gd 2 O 3 , MgO, Sc 2 O 3 , NiO) have been considered as gate insulators in AlGaN/GaN technology, [7][8][9][10][11] with HfO 2 showing remarkably high permittivity values (k > 20). 12,13 Cerium oxide (CeO 2 ) has excellent electrical properties, like a band gap of $6 eV, a high permittivity (k ¼ 15-26), and a critical electric field of 4.9 MV/cm. 14 Although preliminary measurements on metal/CeO 2 /GaN capacitors have been already reported, 15 the implementation of CeO 2 on AlGaN/GaN heterostructures was not demonstrated yet.…”