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

Ga2O3-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 Ga2O3 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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.4\times 10^{{5}}$ </tex-math></inline-formula> with an ultralow dark current of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$3.74\times 10^{-{8}}$ </tex-math></inline-formula> A/cm2, superior to most similar Ga2O3 SBPDs reported to date. Furthermore, without sacrificing the response speed (t<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\text {r}} =100$ </tex-math></inline-formula> ns, t<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\text {d}} = 240.5~\mu $ </tex-math></inline-formula>s), the device attained a peak external quantum efficiency of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.5\times 10^{{4}}$ </tex-math></inline-formula>%. This stems from the ultrahigh photoconductive-like gain caused by significant mobility differences of photogenerated carriers under reverse bias in high-quality Ga2O3 homo-epilayer.