Investigation of traps in halide vapor-phase epitaxy-grown β-Ga₂O₃ epilayers/n⁺-Ga₂O₃ using deep-level transient spectroscopy

Abstract

Detailed investigation of deep traps in 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 milliseconds irrespective of different Schottky metal contacts and epilayers. Two electron traps at E2 (EC–ET =0.65 eV) and E3 (EC–ET =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 have been observed. Below 300 K, a deep trap with a negative DLTS signal peak was also observed at E1 (EC–ET = 0.34 – 0.35 eV) with 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 are found to be unaffected by the electric field during the field-dependence DLTS study. From the filling-pulse width dependence DLTS study, the decrease in capacitance transient amplitude with increasing pulse width has been 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 high at the interface from depth profiling DLTS. Based on the available literature, it is suggested that these traps are related to FeGa, Fe-related centers, and complexes with hydrogen or shallow donors and might be affected or generated during the metallization by the E-beam evaporator and the CMP polishing.