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.