Cr2O3/β-Ga2O3 heterojunction diodes with orientation-dependent breakdown electric field

We report the fabrication of Cr2O3/β-Ga2O3 heterojunction diodes (HJDs) using reactive magnetron sputtering of Cr2O3 on highly doped β-Ga2O3 bulk substrates along (100), (010), (001), (110), and (011) orientation dependence of high electric field handling capability in β-Ga2O3. Additional relative permittivity values in (110) and (011) orientations of β-Ga2O3 were computed by using first-principles calculation methods for accurate apparent charge density (ND–NA) extraction and breakdown electric field analysis from capacitance–voltage measurements. The HJDs fabricated on n+ (110) exhibited breakdown electric fields >10 MV/cm up to 12.9 MV/cm, showing the highest experimentally observed parallel-plane junction electric field among β-Ga2O3-based junctions. Breakdown electric fields among (100), (010), (001), and (011) orientations showed distinct distribution in the range of 5.13–5.26, 5.10–7.05, 2.70–3.33, and 3.88–4.38 MV/cm, respectively, validating the orientational dependence of parallel-plane junction electric field at breakdown in low-symmetry monoclinic β-Ga2O3. The parallel-plane breakdown electric fields (EBr,ǁ) reported in this work were extracted when the device experienced breakdown at 100 mA/cm2 current density compliance, and should not be confused with critical electric field (Ec) as a function of drift layer doping concentration, which accounts for electric-field dependent impact ionization coefficients in Si, SiC, and GaN. This study can guide the choice of crystal orientation for high-performance gallium oxide-based devices that require high electric field handling capability.