High Fill-Factor 4H-SiC Avalanche Photodiodes With Partial Trench Isolation

In this letter, a beveled mesa 4H-SiC ultraviolet (UV) avalanche photodiode (APD) with partial trench isolation is reported. By adopting this partial trench isolation structure, when device diameter of the APD is
$150~\mu \text{m}$
, its fill factor can increase from 33.9% to 63.5% compared with the traditional full trench isolation structure. The photocurrent of the APD shows corresponding improvement when illuminated with the same UV light source. Through current–voltage, spectral response, and single photon detection characterizations, it is proved that the performance of the partial trench isolation APD does not degrade compared with the traditional full trench isolation structure. The APD fabricated in this letter with partial trench isolation shows a unity-gain peak quantum efficiency of 66.4% at 270 nm and a single photon detection efficiency of 9.5% at 280 nm when the dark count rate is fixed at 1 Hz/
$\mu \text{m}^{2}$
.