4H-SiC ultraviolet p-in photodiodes with four different epitaxial structures were fabricated. The experimental results prove that both a thin P +-type Ohmic contact layer and a thick intrinsic layer were indispensible for a high-performance ultraviolet p-in photodiode. A 4H-SiC p-in photodiode with responsivity as high as 0.139 A/W at 278 nm incident wavelength was achieved. Meanwhile, within a certain wavelength range, the peak response wavelength of an ultraviolet p-in photodiode would be modulated by properly varying the thicknesses of P +-type layer and the intrinsic layer. Moreover, the theoretical calculation was carried out to further authorise the experimental results.

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