Ultrahigh Gain at Low Bias Achieved in Homoepitaxial Ga2O3 Schottky Photodiode With Low Dark Current

Ga
₂
O
₃
-based solar-blind photodetectors (SBPDs) with typical Schottky structure usually exhibit low responsivity and rapid saturation as reverse bias increase in the lack of avalanche gain. In this study, large-area photosensitive Ga
₂
O
₃
single-crystalline films were homoepitaxially grown by MOCVD, enabling the fabrication of high-performance SBPDs. At a low bias of -5 V, the device exhibits an ultrahigh photoresponsivity of 27.5 A/W and a photo-to-dark current ratio of 2.4 × 10
⁵
with an ultralow dark current of 3.74 × 10
^-8
A/cm
²
, superior to most similar Ga
₂
O
₃
SBPDs reported to date. Furthermore, without sacrificing the response speed (t
_r
= 100 ns, t
_d
= 240.5 μs), the device attained a peak external quantum efficiency of 1.5 × 10
⁴
%. This stems from the ultrahigh photoconductive-like gain caused by significant mobility differences of photogenerated carriers under reverse bias in high-quality Ga
₂
O
₃
homo-epilayer.