Effects of Doping Concentration on Photoresponse Characteristics of β-Ga<sub>2</sub>O<sub>3</sub> Solar-Blind Photodetectors
Han-Yin Liu, Nianzu Wu, Yi-Ting Wu, Wei-Han Chen, Nei-En Chiu
Abstract
Epitaxial growth of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> -Ga2O3 thin films on <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${c}$ </tex-math></inline-formula> plane sapphire substrates is achieved using mist chemical vapor deposition (mist-CVD) technique, including both undoped and tin-doped variations. Two levels of tin doping are studied (0.1% and 0.3% Sn/(Sn + Ga) ratios). The <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> -Ga2O3 films exhibit monoclinic structure with a single (−201) orientation and a confirmed optical bandgap of 4.9 eV via X-ray diffraction (XRD) and Tauc plot analyses. For the undoped <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> -Ga2O3-based metal–semiconductor–metal (MSM) photodetector (PD), better static photoresponse properties are demonstrated, including low dark current (81.49 ± 9.41 pA at 5 V), high photo-to-dark current ratio (PDCR) ([5.17 ± 0.83] <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times104$ </tex-math></inline-formula> ), UV-to-visible rejection ratio ([7.09 ± 0.86] <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times104$ </tex-math></inline-formula> ), and specific detectivity ([7.71 ± 0.96] <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times1010$ </tex-math></inline-formula> Jones). Using Sn-doped n-type <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> -Ga2O3 degrades these characteristics, yet offers internal photoconductive gain, elevating responsivity (1.34 ± 0.27 A/W). In addition, the dynamic photoresponse in the MSM PD with Sn-doped n-type <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> -Ga2O3 provides a significant persistent photoconductivity (PPC) effect. The present <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> -Ga2O3 MSM PDs are sensitive to 240-nm monochromatic light, showcasing potential for effective solar-blind UV detection.