Picosecond Response Of A Planar GAAS/AL 0.3 GA 0.7 AS Schottky Barrier Photodiode

A high-speed high-sensitivity planar GaAs/AL 0.3 GA 0.7 AS heterostructure Schottky barrier photodiode has been de-signed, fabricated, and characterized. A highly doped A1 0.3 GA 0.7 AS buffer layer is used to reduce the series resistance and the undesired diffusion tailing. Furthermore, surface passivation and antireflection coating, with various dielectric films, are performed to reduce the reverse-bias dark current and the reflection loss of the incident light, thereby significantly improves the sensitivity of the photodiode. The measured external quantum efficiency and responsivity are 60% to 77% and 0.47 A/W to 0.6 A/W, respectively, for the wavelength range of 0.5 μm to 0.84 μm. A risetime of 8.5 ps and a 3-dB cutoff frequency of 50 GHz have been measured.