Performance of 4H-SiC PIN Ultraviolet Avalanche Photodiodes with Different Intrinsic Layer Thicknesses

Four 4H-SiC p-i-n ultraviolet (UV) avalanche photodiode (APD) samples PIN-0.1, PIN-0.35, PIN-0.5, and PIN-1.0 with different intrinsic layer thicknesses (0.1 mu m, 0.35 mu m, 0.5 mu m, and 1.0 mu m, respectively) are designed and fabricated. Single photon detection efficiency (SPDE) performance becomes better as the intrinsic layer thickness increases, which is attributed to the inhibitation of tunneling. Dark count origin is also investigated, an activation energy as small as 0.22 eV of the dark count rate (DCR) confirms that the trap-assisted tunneling (TAT) process is the main source of DCR. The temperature coefficient ranges from -2.6 mV/degrees C to 18.3 mV/degrees C, demonstrating that the TAT process is dominant in APDs with thinner intrinsic layers. Additionally, the room temperature maximum quantum efficiency at 280 nm differs from 48% to 65% for PIN-0.35, PIN-0.5, and PIN-1.0 under 0 V bias, and UV/visible rejection ratios higher than 10(4) are obtained.