p-n heterojunction*

Epitaxial growth of α-Cr₂O₃(p-type) on c-Al2O3 and β-Ga₂O₃ (n-type) on α-Cr₂O₃(p-type) has been carried out to make an all oxide epitaxial n-type β-Ga₂O₃/p-type α-Cr₂O₃ heterojunction using RF sputtering. A valence band offset of 3.38 ± 0.2 eV at the heterojunction is determined using Kraut’s method. From the bandgap measurements of α-Cr₂O₃ and β-Ga₂O₃, the conduction band offset of 1.68 ± 0.2 eV at the heterojunction is obtained. Thus, the band alignment at this heterojunction is found to be staggered (Type-II), which leads to the confinement of electrons and holes in the β-Ga₂O₃ layer and α-Cr₂O₃ layer, respectively. Our results provide a pathway to design all oxide optoelectronic devices based on a p-n heterojunction consisting of n-type β-Ga₂O₃ and p-type α-Cr₂O₃.