Effects of Doping Concentration on Photoresponse Characteristics of β-Ga2O3 Solar-Blind Photodetectors

Epitaxial growth of
$\beta $
-Ga2O3 thin films on
${c}$
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
$\beta $
-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
$\beta $
-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]
$\times104$
), UV-to-visible rejection ratio ([7.09 ± 0.86]
$\times104$
), and specific detectivity ([7.71 ± 0.96]
$\times1010$
Jones). Using Sn-doped n-type
$\beta $
-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
$\beta $
-Ga2O3 provides a significant persistent photoconductivity (PPC) effect. The present
$\beta $
-Ga2O3 MSM PDs are sensitive to 240-nm monochromatic light, showcasing potential for effective solar-blind UV detection.