Abstract: A 4H-SiC avalanche photodetector (APD) with separate absorption and multiplication layers was designed and fabricated.The thicknesses of the absorption and multiplication epilayers were designed as 025 and 1μm,respectively.A multiple junction termination extension (MJTE) was used to eliminate the electric field crowding effect at the edge and to reduce the surface electric field.Dark current,photocurrent,and spectral responsivity were measured.High gain (＞1e4) was achieved at a low breakdown voltage,and the dark current was on the order of about 10pA before device was punched through.The ratio of responsivity at 260nm to that at 380nm was higher than 1e3.A new phenomenon was observed in its spectral responsivity.The response wavelength peak shifted to shorter wavelength as the reverse bias was increased.Near breakdown voltage the peak of the response wavelength was located at 210nm,which was shorter than that at 0V.These results show that the samples have good performance for ultraviolet detection.

Key words: 4H-SiC, ultraviolet, avalanche photodetector