Enhancement-Mode $\beta$ -Ga2O3 Metal–Oxide–Semiconductor Field-Effect Solar-Blind Phototransistor With Ultrahigh Detectivity and Photo-to-Dark Current Ratio

An enhancement-mode <inline-formula> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula>-Ga₂O₃ metal–oxide–semiconductor field-effect solar-blind phototransistor on Si-doped homoepitaxial film grown by molecular beam epitaxy is demonstrated in this letter. Gate-recess process was employed to fully deplete the Ga₂O₃ channel to achieve positive threshold voltage <inline-formula> <tex-math notation="LaTeX">${V}_{{\textsf {th}}}$ </tex-math></inline-formula> (7 V), which broadens the operating range of the solar-blind phototransistor. The dark current of about 0.7 pA is extremely low. Under 254-nm light illumination of 63 <inline-formula> <tex-math notation="LaTeX">$\mu \text{W}$ </tex-math></inline-formula>/cm², the change of drain current reaches more than 6 orders of magnitude. Record high detectivity of 1.3 <inline-formula> <tex-math notation="LaTeX">$\boldsymbol {\times }\,\,10^{{\textsf {16}}}$ </tex-math></inline-formula> Jones and photo-to-dark current ratio of <inline-formula> <tex-math notation="LaTeX">$1.1\,\,{\boldsymbol {\times }}\,\,10^{{\textsf {6}}}$ </tex-math></inline-formula> are obtained, respectively. In addition, the rise and decay time are as short as 100 and 30 ms, respectively. High responsivity of <inline-formula> <tex-math notation="LaTeX">$3\,\,\boldsymbol {\times }\,\, 10^{{\textsf {3}}}$ </tex-math></inline-formula> A/W and external quantum efficiency of <inline-formula> <tex-math notation="LaTeX">$1.5\,\,\boldsymbol {\times }\,\,10^{{\textsf {6}}}$ </tex-math></inline-formula>% are also achieved with apparent solar-blind photodetection.