SiC avalanche photodiodes

We report the fabrication and performance of low-dark-current, high-gain 4H-SiC mesa-structure avalanche photodiodes (APDs). For a photocurrent gain greater than 10 3 the dark current of a 100μm-diameter APD is less than 2nA. The dark current is dominated by surface leakage at the mesa sidewall, which can be significantly reduced by improved sidewall passivation. The unity gain responsivity is 78mA/W at λ=276nm. Two-dimensional raster scans of the photocurrent demonstrate that edge breakdown can be suppressed by employing a 10° sidewall bevel angle. As temperature increases, the breakdown voltage increases relatively slowly with a linearity coefficient of 9mV/°C. Low excess noise, corresponding to k=0.15, is observed. The detectivity (D*) at zero bias is estimated to be as high as 1.6x10 15 cm-Hz 1/2 /W at 276nm.