Investigation of Traps in HVPE Grown β-Ga2O3 Epilayers/n+-Ga2O3 using Deep Level Transient Spectroscopy

A detailed investigation of deep traps in halide vapor-phase epitaxy (HVPE)-grown β-Ga₂O₃ epilayers has been done by performing deep-level transient spectroscopy (DLTS) from 200 K to 500 K on Pt/β-Ga₂O₃ and Ni/β-Ga₂O₃ Schottky diodes. Similar results were obtained with a fill pulse width of 100 ms irrespective of the different Schottky metal contacts and epilayers. Two electron traps at E2 (E _C–E _T = 0.65 eV) and E3 (E _C–E _T = 0.68–0.70 eV) with effective capture cross-sections of 4.10 × 10⁻¹⁴ cm² and 5.75 × 10⁻¹⁵ cm² above 300 K were observed. Below 300 K, a deep trap with a negative DLTS signal peak was also observed at E1 (E _C–E _T = 0.34–0.35 eV) with a very low capture cross-section of 3.28 × 10⁻¹⁷ cm². For a short pulse width of 100 μs, only two electron traps, E2 and E3, at energies of 0.72 eV and 0.73 eV were observed, and one order of higher corresponding effective capture cross-sections. All traps were found to be unaffected by the electric field during the field-dependent DLTS study. From the filling pulse width dependence DLTS study, a decrease in the capacitance transient amplitude with the increasing pulse width was observed opposite to the capture barrier kinetics of the traps and attributed to the emission of carriers during the capture process. Trap concentrations were found to be high at the interface using depth profiling DLTS. Based on the available literature, it is suggested that these traps are related to Fe_Ga, Fe-related centers, and complexes with hydrogen or shallow donors, and might be affected or generated during metallization by the electron beam evaporator and chemical mechanical polishing.