Synergetic Effect of Photoconductive Gain and Persistent Photocurrent in a High-Photoresponse Ga₂O₃Deep-Ultraviolet Photodetector

Abstract

In this work, a metal–semiconductor–metal (MSM) <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> -gallium oxide (Ga2O3) photodetector (PD) was constructed by microprocessing techniques, including UV photolithography, liftoff, and ion beam sputtering. 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 thin film was deposited on a sapphire substrate by a metalorganic chemical vapor deposition method. In addition to the high-quality thin film, the PD showed 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">$3.5\,\,{\times }\,\,10$ </tex-math></inline-formula> 7, a photoresponsivity of 509.78 A/W, a specific detectivity of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$8.79\,\,{\times }\,\,10$ </tex-math></inline-formula> 14 Jones, an external quantum efficiency (EQE) of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.5\,\,{\times }\,\,10$ </tex-math></inline-formula> 5%, and a linear dynamic range of 94.41 dB at 10 V with 254-nm UV light illumination. The PD photoconductive gain decreases with the incident light intensity and reaches up to 2490 under <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2000 ~\mu \text{W}$ </tex-math></inline-formula> cm−2. Such high photoconductive gain due to recycling transport in the active layer may lead to persistent photocurrent. Together with high photoresponsivity and EQE, the substantial internal gain may well exist in 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 PD, suggesting a high deep-ultraviolet photoresponse for 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 MSM photodetector in this article.