Identification of critical buffer traps in Si δ-doped β-Ga2O3 MESFETs

Two buffer traps at E-C-0.7 eV and E-C-0.8 eV have been individually identified as causing threshold voltage and on-resistance instabilities in beta-Ga2O3 Si partial differential -doped transistors grown by plasma-assisted molecular beam epitaxy (PAMBE) on semi-insulating Fe doped beta-Ga2O3 substrates. The instabilities are characterized using double-pulsed current-voltage and isothermal constant drain current deep level transient spectroscopy. The defect spectra are compared between transistors grown using two different unintentionally doped buffer layer thicknesses of 100 nm and 600 nm. The E-C-0.8 eV trap was not seen using the thicker buffer and is shown to correlate with the presence of residual Fe in thePAMBE buffer layer. The E-C-0.7 eV trap was unchanged in concentration and is revealed as the dominating source of the threshold voltage instability. This trap is consistent with the characteristics of a previously reported intrinsic point defect [Ingebrigtsen et al., APL Mater. 7, 022510 (2019)]. The E-C-0.7 eV trap is responsible for similar to 70% of the total threshold voltage shift in the 100 nm thick buffer transistor and 100% in the 600 nm thick buffer transistor, which indicates growth optimization is needed to improve beta-Ga2O3 transistor stability.