Vertical 4H-SiC n-i-p-n APDs With Partial Trench Isolation

In this letter, in order to improve avalanche characteristics in deep ultraviolet range and enhance fill factor, vertical 4H-SiC n-i-p-n avalanche photodiodes (APDs) are designed and fabricated, in which avalanche current flows through a forwardbiased p-n junction formed between the p epi-layer and the n-type substrate. Compared with a traditional n-i-p APD, no obvious difference of gain-voltage and photo-response characteristics is observed, indicating the feasibility of the proposed n-i-p-n device structure. When a partial trench isolation scheme is applied, the vertical n-i-p-n APD shows a high fill factor of 78.3% and a low-bias quantum efficiency of 66%.