Stacked Triple Ultraviolet-Band Metal–Semiconductor–Metal Photodetectors

Abstract

To extend the sensing wavelength band, triple ultraviolet-band metal–semiconductor–metal ultraviolet photodetectors (MSM-UVPDs) were fabricated and studied in this study. Using a radio frequency magnetron sputtering system, the ZnO films, TiO₂ films, and AlN films were sequentially stacked on quartz substrates. The cutoff wavelengths of the ZnO-based, TiO₂-based, and AlN-based MSM-UVPDs were 370, 310, and 220 nm, respectively. The associated photoresponsivity of 47, 142, and 83 mA/W and the associated specific detectivity of <inline-formula> <tex-math notation= LaTeX >$2.02 \\times 10^{10}$ </tex-math></inline-formula>, <inline-formula> <tex-math notation= LaTeX >$9.15 \\times 10^{10}$ </tex-math></inline-formula>, and <inline-formula> <tex-math notation= LaTeX >$2.20 \\times 10^{11}\\,\\,\\text {cm}\\cdot \\text {Hz}^{1/2}\\,\\,\\cdot \\,\\,\\text{W}^{-1}$ </tex-math></inline-formula> were obtained, respectively. By probing the common pad and each UV pad, the performance of the UVA, UVB, and UVC wavelength band could be measured, respectively. The performance of dual-band could be obtained by probing the common pad and the two connected UV pads. Moreover, by probing the common mode and the three connected UV pads in the stacked MSM-UVPDs, the performance of triple ultraviolet bands could be obtained. Because the photoresponsivity in the visible wavelength band was very low, the triple-band MSM-UVPDs can work as solar blind UVPDs. The dominant noise was the flicker noise.