$8\times8$ 4H-SiC Ultraviolet Avalanche Photodiode Arrays With High Uniformity

In this letter, high-uniformity $8\times 8$ arrays of 4H-SiC ultraviolet (UV) avalanche photodiode (APD) are reported. In order to improve the detectivity, large active area ( $300~\mu \text{m}$ diameter) was designed for APD pixels. Thick SiN x dielectric deposited by plasma enhanced chemical vapor deposition (PECVD) was adopted as insulator and passivation layer to suppress the reverse leakage current and premature breakdown. Despite the large active area, a high yield of 97% is achieved for the pixels in the 4H-SiC APD array. At room temperature, the pixels exhibit a high gain of over 105, a maximum quantum efficiency of larger than 68% @ 282 nm and an excellent UV/visible rejection ratio of 104. In addition, temperature-stable avalanche breakdown voltage with a positive coefficient of 8 mV/°C is obtained. Furthermore, the APD array shows a high uniformity of breakdown voltage with a standard deviation of 0.1 V for all the 64 pixels, and the dark currents at 95% of breakdown voltage are as low as ~1 nA except for two pixels. The performance improvements indicate a new milestone for 4H-SiC APD arrays in UV imaging applications.