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

An enhancement-mode
$\beta $
-Ga
₂
O
₃
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 Ga
₂
O
₃
channel to achieve positive threshold voltage
${V}_{{\textsf {th}}}$
(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
$\mu \text{W}$
/cm
²
, the change of drain current reaches more than 6 orders of magnitude. Record high detectivity of 1.3
$\boldsymbol {\times }\,\,10^{{\textsf {16}}}$
Jones and photo-to-dark current ratio of
$1.1\,\,{\boldsymbol {\times }}\,\,10^{{\textsf {6}}}$
are obtained, respectively. In addition, the rise and decay time are as short as 100 and 30 ms, respectively. High responsivity of
$3\,\,\boldsymbol {\times }\,\, 10^{{\textsf {3}}}$
A/W and external quantum efficiency of
$1.5\,\,\boldsymbol {\times }\,\,10^{{\textsf {6}}}$
% are also achieved with apparent solar-blind photodetection.