Ti- and Fe-related charge transition levels in β − Ga 2 O 3

• Published in: Applied physics letters 2020-02, Vol.116 (7)
• Main Authors: Zimmermann, Christian, Frodason, Ymir Kalmann, Barnard, Abraham Willem, Varley, Joel Basile, Irmscher, Klaus, Galazka, Zbigniew, Karjalainen, Antti, Meyer, Walter Ernst, Auret, Francois Danie, Vines, Lasse
• Format: Article
• Language: English
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.5139402

Deep-level transient spectroscopy measurements on β- Ga 2 O 3 crystals reveal the presence of three defect signatures labeled E 2 a ,   E 2 b, and E 3 with activation energies at around 0.66 eV, 0.73 eV, and 0.95 eV below the conduction band edge. Using secondary ion mass spectrometry, a correlation between the defect concentration associated with E 3 and the Ti concentration present in the samples was found. Particularly, it is found that E 3 is the dominant Ti-related defect in β- Ga 2 O 3 and is associated with a single Ti atom. This finding is further corroborated by hybrid functional calculations that predict Ti substituting on an octahedral Ga site, denoted as Ti GaII, to be a good candidate for E 3. Moreover, the deep level transient spectroscopy results show that the level previously labeled E 2 and attributed to Fe substituting on a gallium site ( Fe Ga) consists of two overlapping signatures labeled E 2 a and E 2 b. We tentatively assign E 2 a and E 2 b to Fe substituting for Ga on a tetrahedral or an octahedral site, respectively.