A High Responsivity Self-Powered Solar-Blind DUV Photodetector Based on a Nitrogen-Doped Graphene/β-Ga₂O₃ Microwire p–n Heterojunction

A high responsivity solar-blind deep ultraviolet self-powered photodetector (PD) based on a nitrogen-doped graphene (NGr)/
$\beta $
-Ga
₂
O
₃
microwire p–n heterojunction is reported. Under a 0 V bias and 235 nm (12.2
$\mu \text{W}$
/cm
$^{{2}}$
) light irradiation, the PD shows a light/dark ratio of
$\sim 10^{{5}}$
and a high responsivity of 360 mA/W. Compared with an intrinsic graphene (IGr)/
$\beta $
-Ga
₂
O
₃
heterostructure, the responsivity and light/dark ratio of the p–n heterojunction under a 0 V bias increases by 28 and 100 times, respectively. Under a −20 V bias, the p–n junction has a significantly low dark current of 1.7 pA, which is 100 times smaller than that of the IGr/
$\beta $
-Ga
₂
O
₃
device. This is mainly attributed to the increased built-in electric field between
$\beta $
-Ga
₂
O
₃
and NGr. The downwards shift of the Fermi level in NGr (compared to IGr) and the increased depletion region thickness in
$\beta $
-Ga
₂
O
₃
result in the improved performance of the p–n heterojunction PD.