| UV detection is of great importance in terrestrial applications, UV astronomy, and engine combustion efficiency monitoring. Wide bandgap semiconductors, such as SiC and AlxGa1- xN, are good candidates for UV detector fabrication. Avalanche photodiodes (APDs), which can provide in situ photo-multiplication, are highly desired in photo-detection.; In this study, the design, fabrication and characterization of 4H-SiC APDs have been investigated. The world's first visible blind UV APD and APD linear array based on 4H-SiC have been demonstrated. Three types of 4H-SiC APDs have been designed, fabricated and characterized, which are p-n diodes terminated by the positive bevel with a very small 2° bevel angle, p+-n-n--n + reach through diodes terminated by the modified field plate, and p+-n--n-n--n + reach-through diodes terminated by the multi-step junction termination extension (MJTE). The demonstrated 4H-SiC APDs show quantum efficiency up to 70%, leakage current density lower than 107A/cm 2 at 95% of breakdown, photo-multiplication gain up to 107 , very low excess noise, a response speed less than 2.4ns, positive temperature dependence of the breakdown voltage and capability of operating up to 257°C. The largest device area is 540mum x 540mum. A 40 pixel 4H-SiC APD array has been demonstrated with excellent uniformity in breakdown voltage and good uniformity in the leakage current. The achieved results suggest that 4H-SiC is an excellent candidate for UV avalanche photodiode fabrication.; Based on the fabricated 4H-SiC APDs, the k value, the ratio between the impact ionization rates of electrons and holes, has been experimentally measured for the first time. A k value as low as 0.1 has been measured in case of hole injection domination, indicating that 4H-SiC is an excellent candidate for low excess noise avalanche photodiode fabrication. The impact ionization rates of electrons and holes have been determined based on the photo-current measured at two different wavelengths for the first time. |
