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To extend the wavelength sensing limitation, dual-band ultraviolet photodetectors (UV-PDs) were studied. The ZnO/MgZnO dual-band UV-PDs were constructed by stacking MgZnO nanorods on ZnO films. The wide ultraviolet wavelength from 250 to 360 nm could be detected by the proposed dual-band UV-PDs. When a reverse bias voltage of −5 V was applied on the dual-band UV-PDs, the photoresponsivity at 310 and 360 nm was 196.0 and 0.70 A/W, respectively. The noise equivalent power at 310 and 360 nm was 9.81 × 10−15 W and 2.78 × 10−12 W, respectively. Furthermore, the specific detectivity at 310 and 360 nm was 9.67 × 1013 and 3.41 × 1011 cmHz0.5W−1, respectively.

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By integrating thin film and nanospheres, the metal-semiconductor-metal ultraviolet photodetectors (MSM-UVPDs) were fabricated by stacking tungsten oxide (WO 3 ) nanospheres on WO 3 thin film deposited on sapphire substrates. The sensing cutoff wavelength was 350 nm in the UVA range. Compared the WO 3 nanosphere/WO 3 thin film MSM-UVPDs with the thin-film structured WO 3 MSM-UVPDs, due to the high surface-to-volume ratio of WO 3 nanospheres, the photoresponsivity at a wavelength of 350 nm was improved from 20.7 mA/W to 89.2 mA/W, the noise equivalent power was improved from 2.35 × 10 −10 W to 6.10 × 10 −11 W, and the detectivity was improved from 1.34 × 10 9 cmHz 1/2 W −1 to 5.19 × 10 9 cmHz 1/2 W −1 .