Picosecond Response of A Planar GaAs/Al0.3Ga0.7As Schottky Barrier Photodiode

A high-speed, high-sensitivity planar GaAs/Al0.3Ga0.7As heterostructure Schottky barrier photodiode has been designed, fabricated, and characterized. A highly doped Al0.3Ga0.7As buffer layer is deposited on semi-insulating GaAs substrate to reduce the series resistance and the undesired diffusion tailing of the photodetector. Furthermore, surface passivation and antireflection coatings using various dielectric films are studied to reduce the reverse-bias dark current and the reflection loss of the incident light, thereby significantly improves the sensitivity of the photodiode. The external quantum efficiency of 60% to 70% and responsivity of 0.47 A/W to 0.6 A/W were measured 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 obtained for this detector.